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→Operating systems: That's not FreeBSD-specific; use the Single UNIX Specification as a reference, rather than, for example, using man pages for all of Linux/Darwin/FreeBSD/NetBSD/OpenBSD/DragonFly BSD/Solaris/AIX/HP-UX.
 
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{{short description|Geographical region with a uniform standard time}}
{{Short description|Area that observes a uniform standard time}}
{{About|time zones in general|a list of time zones by country|List of time zones by country|more time zone lists|Lists of time zones|other uses}}
{{Use mdy dates|date=August 2018}}
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{{about|time zones in general|a list of time zones by country|List of time zones by country|more time zone lists|Lists of time zones|other uses}}
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{{refimprove|date=September 2017}}
{{original research|date=August 2018}}
<!-- Note: Please do not use time zone maps that have fixed file names with fixed dates. They are never updated and are only used for historical reference. -->
<!-- Note: Please do not use time zone maps that have fixed file names with fixed dates. They are never updated and are only used for historical reference. -->
{{Use mdy dates|date=March 2024}}
[[File:World Time Zones Map.svg|thumb|right|upright=1.35|Time zones of the world]]


A '''time zone''' is a region of the globe that observes a uniform [[standard time]] for [[legal]], [[Commerce|commercial]], and [[social]] purposes. Time zones tend to follow the boundaries of [[Country|countries]] and their subdivisions because it is convenient for areas in close commercial or other [[communication]] to keep the same [[time]].
A '''time zone''' is an area which observes a uniform [[standard time]] for [[legal]], [[Commerce|commercial]] and [[social]] purposes. Time zones tend to follow the boundaries between [[Country|countries]] and their [[Administrative division|subdivisions]] instead of strictly following [[longitude]], because it is convenient for areas in frequent communication to keep the same time.


Most of the time zones on land are offset from [[Coordinated Universal Time]] (UTC) by a whole number of hours (UTC−12 to UTC+14), but a few zones are offset by 30 or 45 minutes (e.g. [[Newfoundland Time Zone|Newfoundland Standard Time]] is UTC−03:30, [[Nepal Time|Nepal Standard Time]] is UTC+05:45, and [[Indian Standard Time]] is UTC+05:30).
Each time zone is defined by a standard offset from [[Coordinated Universal Time]] (UTC). The offsets range from [[UTC−12:00]] to [[UTC+14:00]], and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes, such as in [[Indian Standard Time|India]] and [[Nepal Time|Nepal]]. Some areas in a time zone may use a different offset for part of the year, typically one hour ahead during [[spring (season)|spring]] and [[summer]], a practice known as [[daylight saving time]] (DST).


{{TOC limit}}
Some higher latitude and [[temperate]] zone countries use [[daylight saving time]] for part of the year, typically by adjusting local clock time by an hour. Many land time zones are skewed toward the west of the corresponding [[nautical time zones]]. This also creates a permanent [[daylight saving]] time effect.


== List of UTC offsets ==
==History==
{{Main|List of UTC time offsets}}
===Early timekeeping===
<!-- Please do not use time zone maps that have fixed file names with fixed dates. They are never updated and are only used for historical reference. -->
Before [[clocks]] were first invented, it was common practice to mark the time of day with [[apparent solar time]] (also called "true" solar time) – for example, the time on a [[sundial]] – which was typically different for every location and dependent on longitude.
[[File:World time zones.svg|800px|thumb|center|Time zones of the world]]


In the table below, the locations that use daylight saving time (DST) are listed in their UTC offset when DST is ''not'' in effect. When DST is in effect, approximately during spring and summer, their UTC offset is increased by one hour (except for [[Lord Howe Island]], where it is increased by 30 minutes). For example, during the DST period [[California]] observes [[UTC−07:00]] and the [[United Kingdom]] observes [[UTC+01:00]].
When well-regulated mechanical clocks became widespread in the early 19th century,<ref>{{Cite book|url=https://www.springer.com/gb/book/9783642293078|title=The Mechanics of Mechanical Watches and Clocks {{!}} Ruxu Du {{!}} Springer|language=en}}</ref><!-- is that the right date?--> each city began to use some local [[mean solar time]]. Apparent and mean solar time can differ by up to around 15 minutes (as described by the [[equation of time]]) because of the elliptical shape of the Earth's orbit around the Sun ([[Orbital eccentricity|eccentricity]]) and the tilt of the Earth's axis ([[Axial tilt|obliquity]]). Mean solar time has days of equal length, and the difference between the two sums to zero after a year.

[[Greenwich Mean Time]] (GMT) was established in 1674, when the [[Royal Observatory, Greenwich|Royal Observatory]] was built, as an aid to mariners to determine [[longitude]] at sea, providing a standard reference time while each city in England kept a different local time.

===Railway time===
[[File:Time zone chicago.jpg|thumb|right|Plaque commemorating the Railway General Time Convention of 1883 in North America]]
Local solar time became increasingly inconvenient as rail transport and telecommunications improved, because clocks differed between places by amounts corresponding to the differences in their geographical longitudes, which varied by four minutes of time for every degree of longitude. For example, [[Bristol]] is about 2.5 degrees west of [[Greenwich]] (East [[London]]), so when it is solar noon in Bristol, it is about 10 minutes past solar noon in London.<ref>Latitude and Longitude of World Cities http://www.infoplease.com/ipa/A0001769.html</ref> The use of time zones accumulates these differences into longer units, usually hours, so that nearby places can share a common standard for timekeeping.

The first adoption of a standard time was on December 1, 1847, in Great Britain by [[History of rail transport in Great Britain|railway companies]] using GMT kept by portable [[marine chronometer|chronometers]]. The first of these companies to adopt standard time was the [[Great Western Railway]] (GWR) in November 1840. This quickly became known as [[Railway time|Railway Time]]. About {{nowrap|August 23, 1852}}, time signals were first transmitted by [[telegraph]] from the Royal Observatory, Greenwich. Even though 98% of Great Britain's public clocks were using GMT by 1855, it was not made Britain's legal time until {{nowrap|August 2, 1880}}. Some British clocks from this period have two minute hands—one for the local time, one for GMT.<ref>{{cite web|url=http://wwp.greenwichmeantime.com/info/bristol-time.htm |title=Bristol Time |publisher=Wwp.greenwichmeantime.com |date= |accessdate=December 5, 2011}}</ref>

Improvements in worldwide communication further increased the need for interacting parties to communicate mutually comprehensible time references to one another. The problem of differing local times could be solved across larger areas by synchronizing clocks worldwide, but in many places that adopted time would then differ markedly from the solar time to which people were accustomed.

On November 2, 1868, the then British colony of New Zealand officially adopted a standard time to be observed throughout the colony, and was perhaps the first country to do so. It was based on the longitude {{nowrap|172°30′}} East of [[Greenwich]], that is 11 hours 30 minutes ahead of GMT. This standard was known as [[Time in New Zealand|New Zealand Mean Time]].<ref>{{cite web|title=Our Time. How we got it. New Zealand's Method. A Lead to the World.|url=http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19290408.2.88&srpos=2|work=Papaerspast|publisher=Evening Post|accessdate=October 2, 2013|page=10}}</ref>

Timekeeping on the American railroads in the mid-19th century was somewhat confused. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time. Some junctions served by several railroads had a clock for each railroad, each showing a different time.<ref>{{Cite web |url=https://www.wired.com/2010/11/1118railroad-time-zones/ |title=Nov. 18, 1883: Railroad Time Goes Coast to Coast |last=Alfred |first=Randy |date=November 18, 2010 |website=Wired |language=en-US |access-date=July 30, 2018}}</ref>

[[File:Time zone map of the United States 1913 (colorized).png|thumb|upright=1.6|right|1913 time zone map of the United States, showing boundaries very different from today]]
[[Charles F. Dowd]] proposed a system of one-hour standard time zones for American railroads about 1863, although he published nothing on the matter at that time and did not consult railroad officials until 1869. In 1870 he proposed four ideal time zones (having north–south borders), the first centered on [[Washington, D.C.]], but by 1872 the first was centered on the meridian [[75th meridian west|75° W of Greenwich]], with geographic borders (for example, sections of the [[Appalachian Mountains]]). Kalepalli's system was never accepted by American railroads. Instead, U.S. and Canadian railroads implemented a version proposed by William F. Allen, the editor of the ''Traveler's Official Railway Guide''.<ref>{{cite web |url= http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |title= Economics of Time Zones |deadurl= yes |archiveurl= https://web.archive.org/web/20120514014456/http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |archivedate= May 14, 2012 |df= }} &nbsp;{{small|(1.89&nbsp;MB)}} </ref> The borders of its time zones ran through railroad stations, often in major cities. For example, the border between its Eastern and Central time zones ran through [[Detroit]], [[Buffalo, New York|Buffalo]], [[Pittsburgh]], [[Atlanta]], and [[Charleston, South Carolina|Charleston]]. It was inaugurated on Sunday, {{nowrap|November 18, 1883}}, also called "The Day of Two Noons",<ref>{{cite web|url=http://historymatters.gmu.edu/d/5748 |title=Historymatters.gmu.edu |publisher=Historymatters.gmu.edu |date= |accessdate=December 5, 2011}}</ref> when each railroad station clock was reset as standard-time noon was reached within each time zone. The zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within a year 85% of all cities with populations over 10,000, about 200 cities, were using standard time.<ref>{{cite web|url=http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |title=Resolution concerning new standard time by Chicago |publisher=Sos.state.il.us |date= |accessdate=December 5, 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20111005050317/http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |archivedate=October 5, 2011 }} </ref> A notable exception was Detroit (which is about halfway between the meridians of eastern time and central time) which kept local time until 1900, then tried Central Standard Time, [[local mean time]], and [[Eastern Time Zone|Eastern Standard Time]] before a May 1915 ordinance settled on EST and was ratified by popular vote in August 1916. The confusion of times came to an end when Standard zone time was formally adopted by the [[United States Congress|U.S. Congress]] in the [[Standard Time Act]] of March 19, 1918.

===Worldwide time zones===
{{refimprove section|date=August 2015}}
The first known person to conceive of a worldwide system of time zones was the Italian mathematician [[Quirico Filopanti]]. He introduced the idea in his book ''Miranda!'' published in 1858. He proposed 24 hourly time zones, which he called "longitudinal days", the first centred on the meridian of Rome. He also proposed a universal time to be used in astronomy and telegraphy. But his book attracted no attention until long after his death.<ref>[http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html Quirico Filopanti] from scienzagiovane, Bologna University, Italy. {{webarchive |url=https://web.archive.org/web/20130117011106/http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html |date=January 17, 2013 }} </ref><ref>Gianluigi Parmeggiani (Osservatorio Astronomico di Bologna),
[http://www.iav.it/planetario/didastro/didastro/english.htm The origin of time zones] {{webarchive |url=https://web.archive.org/web/20070824155341/http://www.iav.it/planetario/didastro/didastro/english.htm |date=August 24, 2007 }} </ref>

Scottish-born Canadian Sir [[Sandford Fleming]] proposed a worldwide system of time zones in 1879. He advocated his system at several international conferences, and is credited with "the initial effort that led to the adoption of the present time meridians".<ref>{{cite web|url=http://www.webexhibits.org/daylightsaving/d.html |title=History & info - Standard time began with the railroads|website=www.webexhibits.org|accessdate=February 13, 2018}}</ref> In 1876, his first proposal was for a global 24-hour clock, conceptually located at the centre of the Earth and not linked to any surface meridian. In 1879 he specified that his universal day would begin at the anti-meridian of Greenwich ([[180th meridian]]), while conceding that hourly time zones might have some limited local use. He also proposed his system at the [[International Meridian Conference]] in October 1884, but it did not adopt his time zones because they were not within its purview. The conference did adopt a universal day of 24 hours beginning at Greenwich midnight, but specified that it "shall not interfere with the use of local or standard time where desirable".<ref name=imc>{{citation |title=International conference held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884. Protocols of the proceedings. |url=https://babel.hathitrust.org/cgi/pt?id=nyp.33433084034655;view=1up;seq=209 |accessdate=July 23, 2018 |year=1884 |page=201}}</ref>

By about 1900, almost all time on Earth was in the form of standard time zones, only some of which used an hourly offset from GMT. Many applied the time at a local astronomical observatory to an entire country, without any reference to GMT. It took many decades before all time on Earth was in the form of time zones referred to some "standard offset" from GMT/UTC. By 1929, most major countries had adopted hourly time zones. [[Nepal]] was the last country to adopt a standard offset, shifting slightly to UTC+5:45 in 1956.<ref>{{Cite web|url=http://archive.nepalitimes.com/news.php?id=10013#.Vsy33cdh23U|title=15 minutes of fame - Nepali Times|website=archive.nepalitimes.com|access-date=August 22, 2018}}</ref>

Today, all nations use standard time zones for secular purposes, but they do not all apply the concept as originally conceived. [[Newfoundland and Labrador|Newfoundland]], India, Iran, Afghanistan, Burma, Sri Lanka, the [[Marquesas Islands|Marquesas]], as well as parts of Australia use half-hour deviations from standard time, and some nations, such as Nepal, and some provinces, such as the [[Chatham Islands]] of New Zealand, use quarter-hour deviations. Some countries, such as China and India, use a single time zone even though the extent of their territory far exceeds 15° of longitude.<ref>{{Cite news|url=https://www.theatlantic.com/china/archive/2013/11/china-only-has-one-time-zone-and-thats-a-problem/281136/|title=China Only Has One Time Zone—and That's a Problem|last=Schiavenza|first=Matt|date=November 5, 2013|work=The Atlantic|access-date=August 22, 2018|language=en-US}}</ref>

==Notation of time==

===ISO 8601===
{{main article|ISO 8601}}
ISO 8601 is an [[International Organization for Standardization|international standard]] that defines methods of representing dates and times in textual form, including specifications for representing time zones.<ref>{{Cite news|url=https://www.atlasobscura.com/articles/map-mondays-wtf-is-wrong-with-canada-s-time|title=In Canada, You Can Just Write the Date Whichever Way You Want|date=June 8, 2015|work=Atlas Obscura|access-date=August 22, 2018|language=en}}</ref>

===UTC===
If a time is in [[Coordinated Universal Time]] (UTC), a "Z" is added directly after the time without a separating space. "Z" is the zone designator for the zero UTC offset. "09:30&nbsp;UTC" is therefore represented as "09:30Z" or "0930Z". Likewise, "14:45:15&nbsp;UTC" is written as "14:45:15Z" or "144515Z".<ref>{{Cite web|url=https://www.timeanddate.com/time/zones/z|title=Z – Zulu Time Zone (Time Zone Abbreviation)|website=www.timeanddate.com|language=en|access-date=August 22, 2018}}</ref>

UTC time is also known as "Zulu" time, since "Zulu" is a [[ICAO spelling alphabet|phonetic alphabet]] code word for the letter "Z".<ref>{{Cite web|url=https://www.timeanddate.com/time/zones/z|title=Z – Zulu Time Zone (Time Zone Abbreviation)|website=www.timeanddate.com|language=en|access-date=August 22, 2018}}</ref>

====Offsets from UTC====
[[UTC offset|Offsets from UTC]] are written in the format ±[hh]:[mm], ±[hh] [mm], or ±[hh] (either hours ahead or behind UTC). For example, if the time being described is one hour ahead of UTC (such as the time in [[Berlin]] during the winter), the zone designator would be "[[UTC+01:00|+01:00]]", "+0100", or simply "+01". This numeric representation of time zones is appended to local times in the same way that alphabetic time zone abbreviations (or "Z", as above) are appended. The offset from UTC changes with [[daylight saving time]], e.g. a time offset in [[Chicago]], which is in the [[Central Time Zone (North America)|North American Central Time Zone]], is "[[UTC−06:00|−06:00]]" for the winter (Central Standard Time) and "[[UTC−05:00|−05:00]]" for the summer (Central Daylight Time).<ref>{{Cite web|url=https://www.nhc.noaa.gov/aboututc.shtml|title=What is UTC or GMT Time?|website=www.nhc.noaa.gov|access-date=August 22, 2018}}</ref>

===Abbreviations===
{{Main article|List of time zone abbreviations}}
Time zones are often represented by alphabetic abbreviations such as "EST", "WST", and "CST", but these are not part of the international time and date standard [[ISO 8601#Time zone designators|ISO 8601]] and their use as sole designator for a time zone is discouraged. Such designations can be ambiguous; for example, "ECT" could be interpreted as "Eastern Caribbean Time" (UTC−4h), "Ecuador Time" (UTC−5h), or "European Central Time" (UTC+1h).<ref>{{Cite web|url=http://www.pixelbeat.org/docs/linux_timezones/|title=Time zone ambiguities on Linux|website=www.pixelbeat.org|access-date=August 22, 2018}}</ref>

==UTC offsets worldwide==
{{Main article|List of UTC time offsets}}
{| style="margin:auto;"
|-
|[[File:Standard World Time Zones.png|thumb|800px|center]]<!-- Note: Please do not use time zone maps that have fixed file names with fixed dates. They are never updated and are only used for historical reference. -->
|-
|[[File:Solar time vs standard time.png|thumb|800px|center|A great part of the world has a gap between the official time and the solar time]]
|-
|[[File:UTC hue4map X world Robinson.png|800px|thumb|center]]
{| class="wikitable" style="width:800px;"
|-
! colspan=4 style="width:160px"|UTC−12:00 ...<br />UTC−07:00
! colspan=4 style="width:160px"|UTC−06:00 ...<br />UTC−01:00
! colspan=4 style="width:160px"|UTC±00:00 ...<br />UTC+05:45
! colspan=4 style="width:160px"|UTC+06:00 ...<br />UTC+11:30
! colspan=4 style="width:160px"|UTC+12:00 ...<br />UTC+14:00
|-
| colspan=4 | Oceania / North America / [[Time in Antarctica|Antarctica]]
| colspan=4 | North and South America / [[Time in Antarctica|Antarctica]]
| colspan=4 | [[Time in Europe|Europe]] / Africa / Asia / [[Time in Antarctica|Antarctica]]
| colspan=4 | Asia / [[Time in Antarctica|Antarctica]]
| colspan=4 | Asia / Oceania / [[Time in Antarctica|Antarctica]]
|-
| colspan=2|No DST in summer
| colspan=2|DST in summer
| colspan=2|No DST in summer
| colspan=2|DST in summer
| colspan=2|No DST in summer
| colspan=2|DST in summer
| colspan=2|No DST in summer
| colspan=2|DST in summer
| colspan=2|No DST in summer
| colspan=2|DST in summer
|-
| style="background:#f00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC−12:00|−12:00]]
| style="background:#c00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC−12:00|−12:00]]<br />/[[UTC−11:00|−11:00]]<br />N: [[Time in the United States|US]]-
| style="background:#f00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC−06:00|−06:00]]
| style="background:#c00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC−06:00|−06:00]]<br />/[[UTC−05:00|−05:00]]<br />N: [[Time in the United States|US]]-, [[Time in Mexico|MX]]-
| style="background:#f00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC±00:00|±00:00]]<br />[[Iceland|IS]]
| style="background:#c00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC±00:00|±00:00]]<br />/[[UTC+01:00|+01:00]]<br />N: [[Time in the United Kingdom|GB]], [[Time in the Republic of Ireland|IE]], PT
| style="background:#f00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC+06:00|+06:00]]<br />[[Time in Russia|RU]]-, [[Kazakhstan|KZ-]]-
| style="background:#c00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC+06:00|+06:00]]<br />/[[UTC+07:00|+07:00]]
| style="background:#f00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC+12:00|+12:00]]<br />[[Kiribati|KI]]-, [[Time in Russia|RU]]-
| style="background:#c00; width:5px;"|
| style="vertical-align:top;width:75px" | [[UTC+12:00|+12:00]]<br />/[[UTC+13:00|+13:00]]<br />S: [[Time in New Zealand|NZ]]-
|-
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| style="background:#ff8000" |
| style="vertical-align:top;" | [[UTC+06:30|+06:30]]<br />[[Myanmar|MM]]
| style="background:#c60;"|
| style="vertical-align:top;" |
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| style="background:#ffbf00" |
| style="vertical-align:top;" | [[UTC+12:45|+12:45]]
| style="background:#c90;"|
| style="vertical-align:top;" | [[UTC+12:45|+12:45]]<br />/[[UTC+13:45|+13:45]]<br />S: [[Time in New Zealand|NZ]]
|-
| style="background:#ff0;"|
| style="vertical-align:top;" | [[UTC−11:00|−11:00]]<br />[[Time in the United States|US]]-
| style="background:#cc0;"|
| style="vertical-align:top;" | [[UTC−11:00|−11:00]]<br />/[[UTC−10:00|−10:00]]
| style="background:#ff0;"|
| style="vertical-align:top;" | [[UTC−05:00|−05:00]]<br />BO, CO, PA, PE
| style="background:#cc0;"|
| style="vertical-align:top;" | [[UTC−05:00|−05:00]]<br />/[[UTC−04:00|−04:00]]<br />N: [[Time in Canada|CA]]-, CU, [[Time in the United States|US]]-
| style="background:#ff0;"|
| style="vertical-align:top;" | [[UTC+01:00|+01:00]]<br />TN, CG, CD-, DZ, [[Niger|NE]], [[Nigeria|NG]]
| style="background:#cc0;"|
| style="vertical-align:top;" | [[UTC+01:00|+01:00]]<br />/[[UTC+02:00|+02:00]]<br />N: AT, BA, BE, CH, CZ, [[Time in Germany|DE]], DK, ES-, FR, HR, HU, IT, LI, LU, MK, NL, NO, PL, SE, SI, SK<br />S: [[Namibia|NA]]
| style="background:#ff0;"|
| style="vertical-align:top;" | [[UTC+07:00|+07:00]]<br />[[Time in Russia|RU]]-, VN, LA, TH, KH, [[Time in Indonesia|ID]]-
| style="background:#cc0;"|
| style="vertical-align:top;" | [[UTC+07:00|+07:00]]<br />/[[UTC+08:00|+08:00]]<br />N: [[Time in Mongolia|MN]]-
| style="background:#ff0;"|
| style="vertical-align:top;" | [[UTC+13:00|+13:00]]<br />[[Kiribati|KI]]-
| style="background:#cc0;"|
|
|-
| style="background:#0f0;"|
| style="vertical-align:top;" | [[UTC−10:00|−10:00]]<br />[[Time in the United States|US]]-
| style="background:#0c0;"|
| style="vertical-align:top;" | [[UTC−10:00|−10:00]]<br />/[[UTC−09:00|−09:00]]<br />[[Time in the United States|US]]-
| style="background:#0f0;"|
| style="vertical-align:top;" | [[UTC−04:00|−04:00]]
| style="background:#0c0;"|
| style="vertical-align:top;" | [[UTC−04:00|−04:00]]<br />/[[UTC−03:00|−03:00]]<br />S: [[Time in Chile|CL]]-
| style="background:#0f0;"|
| style="vertical-align:top;" | [[UTC+02:00|+02:00]]<br />Africa: [[Burundi|BI]], [[Botswana|BW]], [[Democratic Republic of the Congo|CD]]-, [[Egypt|EG]], [[Libya|LY]], [[Malawi|MW]], [[Mozambique|MZ]], [[Rwanda|RW]], [[South Africa|ZA]], [[Zambia|ZM]], [[Zimbabwe|ZW]]
| style="background:#0c0;"|
| style="vertical-align:top;" | [[UTC+02:00|+02:00]]<br />/[[UTC+03:00|+03:00]]<br />N: [[Finland|FI]], [[Estonia|EE]], [[Latvia|LV]], [[Lithuania|LT]], [[Ukraine|UA]], BG, [[Greece|GR]], MD, [[Romania|RO]]
| style="background:#0f0;"|
| style="vertical-align:top;" | [[UTC+08:00|+08:00]]<br />[[Time in Australia|AU]]-, CN, HK, [[Time in Indonesia|ID]], MY, [[Time in Russia|RU]]-, [[Time in the Philippines|PH]], SG, TW,
| style="background:#0c0;"|
| style="vertical-align:top;" | [[UTC+08:00|+08:00]]<br />/[[UTC+09:00|+09:00]]<br />N: [[Time in Mongolia|MN]]-
| style="background:#0f0;"|
| style="vertical-align:top;" | [[UTC+14:00|+14:00]]<br />[[Kiribati|KI]]-
| style="background:#0c0;"|
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| style="background:#00ff80" |
| style="vertical-align:top;" | [[UTC−03:30|−03:30]]
| style="background:#0c6;"|
| style="vertical-align:top;" | [[UTC−03:30|−03:30]]<br />/[[UTC−02:30|−02:30]]<br />S: [[Time in Canada|CA]]-
|
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|-
| style="background:#0ff;"|
| style="vertical-align:top;" | [[UTC−09:00|−09:00]]
| style="background:#0cc;"|
| style="vertical-align:top;" | [[UTC−09:00|−09:00]]<br />/[[UTC−08:00|−08:00]]<br />N: [[Time in the United States|US]]-
| style="background:#0ff;"|
| style="vertical-align:top;" | [[UTC−03:00|−03:00]]<br />S: [[Time in Argentina|AR]]<br />[[Time in Chile|CL]]-
| style="background:#0cc;"|
| style="vertical-align:top;" | [[UTC−03:00|−03:00]]<br />/[[UTC−02:00|−02:00]]<br />S: [[Time in Brazil|BR]]-
| style="background:#0ff;"|
| style="vertical-align:top;" | [[UTC+03:00|+03:00]]<br />Europe: [[Belarus|BY]], [[Time in Russia|RU]]-, [[Turkey|TR]], Africa: KE, SD, SO, SS, ER, Asia: IQ, SA
| style="background:#0cc;"|
| style="vertical-align:top;" | [[UTC+03:00|+03:00]]<br />/[[UTC+04:00|+04:00]]
| style="background:#0ff;"|
| style="vertical-align:top;" | [[UTC+09:00|+09:00]]<br />[[Time in Russia|RU]]-, [[Time in Japan|JP]], [[Time in South Korea|KR]], [[Time in Indonesia|ID]]-
| style="background:#0cc;"|
| style="vertical-align:top;" | [[UTC+09:00|+09:00]]<br />/[[UTC+10:00|+10:00]]
|-
|
|
|
|
|
|
|
|
| style="background:#0080ff" |
| style="vertical-align:top;" | [[UTC+03:30|+03:30]]
| style="background:#06c;"|
| style="vertical-align:top;" | [[UTC+03:30|+03:30]]<br />/[[UTC+04:30|+04:30]]<br />[[Iran|IR]]
| style="background:#0080ff" |
| style="vertical-align:top;" | [[UTC+09:30|+09:30]]
| style="background:#06c;"|
| style="vertical-align:top;" | [[UTC+09:30|+09:30]]<br />/[[UTC+10:30|+10:30]]<br />[[Time in Australia|AU]]-
|-
| style="background:#00f;"|
| style="vertical-align:top;" | [[UTC−08:00|−08:00]]
| style="background:#00c;"|
| style="vertical-align:top;" | [[UTC−08:00|−08:00]]<br />/[[UTC−07:00|−07:00]]<br />N: [[Time in Canada|CA]]-, [[Time in the United States|US]]-, [[Time in Mexico|MX]]-
| style="background:#00f;"|
| style="vertical-align:top;" | [[UTC−02:00|−02:00]]<br />[[Time in Brazil|BR]]-
| style="background:#00c;"|
| style="vertical-align:top;" | [[UTC−02:00|−02:00]]<br />/[[UTC−01:00|−01:00]]
| style="background:#00f;"|
| style="vertical-align:top;" | [[UTC+04:00|+04:00]]<br />[[Time in Russia|RU]]-, [[Time in Georgia (country)|GE]]
| style="background:#00c;"|
| style="vertical-align:top;" | [[UTC+04:00|+04:00]]<br />/[[UTC+05:00|+05:00]]
| style="background:#00f;"|
| style="vertical-align:top;" | [[UTC+10:00|+10:00]]<br />[[Time in Russia|RU]]-
| style="background:#00c;"|
| style="vertical-align:top;" | [[UTC+10:00|+10:00]]<br />/[[UTC+11:00|+11:00]]
|-
|
|
|
|
|
|
|
|
| style="background:#8000ff" |
| style="vertical-align:top;" | [[UTC+04:30|+04:30]]<br />[[Afghanistan|AF]]
| style="background:#60c;"|
|
|
|
|
|
|-
| style="background:#f0f;"|
| style="vertical-align:top;" | [[UTC−07:00|−07:00]]<br />[[Time in the United States|US]]-, [[Time in Mexico|MX]]-
| style="background:#c0c;"|
| style="vertical-align:top;" | [[UTC−07:00|−07:00]]<br />/[[UTC−06:00|−06:00]]<br />N: [[Time in Canada|CA]]-, [[Time in the United States|US]]-, [[Time in Mexico|MX]]-<br />S: [[Time in Chile|CL]]-
| style="background:#f0f;"|
| style="vertical-align:top;" | [[UTC−01:00|−01:00]]
| style="background:#c0c;"|
| style="vertical-align:top;" | [[UTC−01:00|−01:00]]<br />/[[UTC±00:00|±00:00]]
| style="background:#f0f;"|
| style="vertical-align:top;" | [[UTC+05:00|+05:00]]<br />[[Time in Kazakhstan|KZ]]-, PK
| style="background:#c0c;"|
| style="vertical-align:top;" | [[UTC+05:00|+05:00]]<br />/[[UTC+06:00|+06:00]]
| style="background:#f0f;"|
| style="vertical-align:top;" | [[UTC+11:00|+11:00]]<br />[[Time in Russia|RU]]-
| style="background:#c0c;"|
| style="vertical-align:top;" | [[UTC+11:00|+11:00]]<br />/[[UTC+12:00|+12:00]]
|-
|
|
|
|
|
|
|
|
| style="background:#ff0080" |
| style="vertical-align:top;" | [[UTC+05:30|+05:30]]<br />[[Time in India|IN]]
| style="background:#c06;"|
|
| style="background:#ff0080" |
| style="vertical-align:top;" | [[UTC+11:30|+11:30]]<br />[[Norfolk Island|NF]]
| style="background:#c06;"|
|
|-
|
|
|
|
|
|
|
|
| style="background:#ff0040" |
| style="vertical-align:top;" | [[UTC+05:45|+05:45]]<br />[[Nepal|NP]]
| style="background:#cc0020;" |
|
|
|
|
|
|}
XX = [[ISO 3166-1 alpha-2]] country code, XX- = parts of the country, N = North, S = South, UTC = [[Universal Coordinated Time]], DST = [[Daylight Saving Time]]
]]
|}


{| class="wikitable" style="font-size:90%; line-height:1.2"
==List of UTC offsets==
{{merge from|List of UTC time offsets|discuss=Talk:Time zone#Merger proposal|date=May 2018}}
These examples give the local time at various locations around the world when daylight saving time is not in effect:
<!-- If a country has just one time zone list the country, not its capital.
If a state or province has just one time zone list the state or province, not its largest city.
This is not the place to write every single location that lies in a particular zone. This is just for a few examples. Please, do not fill said table with more locations. -->
{| class="wikitable" style="margin: 1em auto 1em auto"
|-
|-
! Time offset
! UTC offset
! colspan=2|Locations that do not use DST
! style="width:200px;" | Example time<br />([[ISO 8601]] notation)
! Example locations that do not use DST
! colspan=2|Locations that use DST
! Example locations that in summer use DST
|-
|-
| [[UTC−12:00]]
| [[UTC−12:00]]
| style=background:#00FF85| ||style=width:40%|<div style="column-width:10em;column-count:2">{{flag|Baker Island}}<br>{{flag|Howland Island}}</div>
| {{TimebyUTCoffset|-|12|00}}
| style=background:#00BF63| ||style=width:60%|
| [[Baker Island]], [[Howland Island]] (both uninhabited)
|
|-
|-
| [[UTC−11:00]]
| [[UTC−11:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|American Samoa}}<br>{{flag|Jarvis Island}}<br>{{flag|Kingman Reef}}<br>{{flag|Midway Atoll}}<br>{{flag+link|Time in|Niue}}<br>{{flag|Palmyra Atoll}}</div>
| {{TimebyUTCoffset|-|11|00}}
| style=background:#D3D800| ||
| {{flagicon|American Samoa}} [[American Samoa]], {{flagicon|Niue}} [[Niue]]
|
|-
|-
| [[UTC−10:00]]
| [[UTC−10:00]]
| style=background:#FF409C| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Cook Islands}}<br>{{no col break|{{flag|French Polynesia}} (most)}}{{flag|Johnston Atoll}}<br>{{flag+link|Time in|United States}}: [[Time in Hawaii|Hawaii]]</div>
| {{TimebyUTCoffset|-|10|00}}
| style=background:#DE006A| ||{{flag+link|Time in|United States}}: [[Andreanof Islands]], [[Islands of Four Mountains]], [[Near Islands]], [[Rat Islands]] ([[Aleutian Islands]], [[Alaska]])
| {{flagicon|French Polynesia}} [[French Polynesia]] (most), {{flagicon|USA}} [[Time in the United States|United States]] {{flagicon|Hawaii}} ([[Hawaii]])
| {{flagicon|USA}} [[Time in the United States|United States]] ([[Aleutian Islands]])
|-
|-
| [[UTC−09:30]]
| [[UTC−09:30]]
| style=background:#CD61FF| ||{{flag|French Polynesia}}: [[Marquesas Islands]]
| {{TimebyUTCoffset|-|09|30}}
| style=background:#9900E0| ||
| {{flagicon|French Polynesia}} [[French Polynesia]] ([[Marquesas Islands]])
|
|-
|-
| [[UTC−09:00]]
| [[UTC−09:00]]
| style=background:#6D6AFF| ||{{flag|French Polynesia}}: [[Gambier Islands]]
| {{TimebyUTCoffset|-|09|00}}
| style=background:#0400CD| ||{{flag+link|Time in|United States}}: [[Time in Alaska|Alaska]] (most)
| {{flagicon|French Polynesia}} [[French Polynesia]] ([[Gambier Islands]])
| {{flagicon|USA}} [[Time in the United States|United States]] {{flagicon|Alaska}} (most of [[Alaska]])
|-
|-
| [[UTC−08:00]]
| [[UTC−08:00]]
| style=background:#00FF85| ||{{flag|Clipperton Island}}<br>{{flag|Pitcairn Islands}}
| {{TimebyUTCoffset|-|08|00}}
| style=background:#00BF63| ||<div style="column-width:20em;column-count:2">{{flag+link|Time in|Canada}}: [[British Columbia]] (most)<br>{{flag+link|Time in|Mexico}}: [[Baja California]]<br>{{flag+link|Time in|United States}}: [[Time in California|California]], [[Time in Idaho|Idaho]] (north), [[Time in Nevada|Nevada]] (most), [[Time in Oregon|Oregon]] (most), [[Washington (state)|Washington]]</div>
| [[Pitcairn Islands]]
| {{flagicon|CAN}} [[Time in Canada|Canada]] {{flagicon|British Columbia}} (most of [[British Columbia]]), {{flagicon|MEX}} [[Time in Mexico|Mexico]] {{flagicon|Baja California}} ([[Baja California]]), {{flagicon|USA}} [[Time in the United States|United States]] {{flagicon|California}} ([[California]], {{flagicon|Nevada}} most of [[Nevada]], {{flagicon|Oregon}} most of [[Oregon]], {{flagicon|Washington (state)}} [[Washington (state)|Washington]])
|-
|-
| [[UTC−07:00]]
| [[UTC−07:00]]
| style=background:#F0FF00| ||{{flag+link|Time in|Canada}}: [[British Columbia]] (northeast), [[Yukon]]<br>{{flag+link|Time in|Mexico}}: [[Baja California Sur]], [[Nayarit]] (most), [[Sinaloa]], [[Sonora]]<br>{{flag+link|Time in|United States}}: [[Time in Arizona|Arizona]] (most)
| {{TimebyUTCoffset|-|07|00}}
| style=background:#D3D800| ||{{flag+link|Time in|Canada}}: [[Alberta]], [[British Columbia]] (southeast), [[Northwest Territories]], [[Time in Nunavut|Nunavut]] (west), [[Time in Saskatchewan|Saskatchewan]] ([[Lloydminster]] area)<br>{{flag+link|Time in|Mexico}}: [[Chihuahua (state)|Chihuahua]] (northwest border)<br>{{flag+link|Time in|United States}}: [[Time in Arizona|Arizona]] ([[Navajo Nation]]), [[Colorado]], [[Time in Idaho|Idaho]] (most), [[Time in Kansas|Kansas]] (west), [[Montana]], [[Time in Nebraska|Nebraska]] (west), [[New Mexico]], [[Time in Nevada|Nevada]] (northeast border), [[Time in North Dakota|North Dakota]] (southwest), [[Time in Oregon|Oregon]] (east), [[Time in South Dakota|South Dakota]] (west), [[Time in Texas|Texas]] (west), [[Utah]], [[Wyoming]]
| {{flagicon|CAN}} [[Time in Canada|Canada]] {{flagicon|British Columbia}} (northeastern [[British Columbia]]), {{flagicon|MEX}} [[Time in Mexico|Mexico]] {{flagicon|Sonora}} ([[Sonora]]), {{flagicon|USA}} [[Time in the United States|United States]] {{flagicon|Arizona}} (most of [[Arizona]])
| {{flagicon|CAN}} [[Time in Canada|Canada]] {{flagicon|Alberta}} ([[Alberta]]), {{flagicon|MEX}} [[Time in Mexico|Mexico]] {{flagicon|Chihuahua (state)}} ([[Chihuahua (state)|Chihuahua]]), {{flagicon|USA}}[[Time in the United States|United States]] {{flagicon|Colorado}}([[Colorado]])
|-
|-
| [[UTC−06:00]]
| [[UTC−06:00]]
| style=background:#FF409C| ||<div style="column-width:10em;column-count:2">{{flag|Belize}}<br>{{flag+link|Time in|Canada}}: [[Time in Saskatchewan|Saskatchewan]] (most)<br>{{flag+link|Time in|Costa Rica}}<br>{{no col break|{{flag+link|Time in|Ecuador}}: [[Galápagos Province|Galápagos]]}}{{flag|El Salvador}}<br>{{flag|Guatemala}}<br>{{flag|Honduras}}<br>{{flag+link|Time in|Mexico}} (most)<br>{{flag|Nicaragua}}</div>
| {{TimebyUTCoffset|-|06|00}}
| style=background:#DE006A| ||<div style="column-width:20em;column-count:2">{{flag+link|Time in|Canada}}: [[Manitoba]], [[Time in Nunavut|Nunavut]] (central), [[Ontario]] (west)<br>{{flag+link|Time in|Chile}}: [[Easter Island]]<br>{{flag+link|Time in|Mexico}} (northeast border)<br>{{no col break|{{flag+link|Time in|United States}}: [[Time in Alabama|Alabama]], [[Arkansas]], [[Time in Florida|Florida]] (northwest), [[Illinois]], [[Time in Indiana|Indiana]] (northwest, southwest), [[Iowa]], [[Time in Kansas|Kansas]] (most), [[Time in Kentucky|Kentucky]] (west), [[Louisiana]], [[Time in Michigan|Michigan]] (northwest border), [[Minnesota]], [[Mississippi]], [[Missouri]], [[Time in Nebraska|Nebraska]] (most), [[Time in North Dakota|North Dakota]] (most), [[Oklahoma]], [[Time in South Dakota|South Dakota]] (most), [[Time in Tennessee|Tennessee]] (most), [[Time in Texas|Texas]] (most), [[Wisconsin]]}}</div>
| {{BIZ}}, {{flagicon|CAN}}[[Time in Canada|Canada]] {{flagicon|Saskatchewan}}(most of [[Saskatchewan]]), {{CRC}}, {{ECU}} ([[Galápagos Islands]]), {{ESA}}, {{GUA}}, {{HON}}, {{NCA}}
| {{flagicon|CAN}} [[Time in Canada|Canada]] {{flagicon|Manitoba}}([[Manitoba]]), {{flagicon|USA}}[[Time in the United States|United States]] ({{flagicon|Illinois}}[[Illinois]], {{flagicon|Texas}}most of [[Texas]]), {{flagicon|MEX}}[[Time in Mexico|Mexico]] (most), {{flagicon|CHI}}[[Time in Chile|Chile]] {{flagicon|Easter Island}}([[Easter Island]])
|-
|-
| [[UTC−05:00]]
| [[UTC−05:00]]
| style=background:#6D6AFF| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Brazil}}: [[Acre (state)|Acre]], [[Amazonas (Brazilian state)|Amazonas]] (southwest)<br>{{flag+link|Time in|Canada}}: [[Atikokan]], [[Mishkeegogamang First Nation|Mishkeegogamang]], [[Southampton Island]]<br>{{flag|Cayman Islands}}<br>{{flag+link|Time in|Colombia}}<br>{{flag+link|Time in|Ecuador}} (most)<br>{{flag+link|Time in|Jamaica}}<br>{{flag+link|Time in|Mexico}}: [[Quintana Roo]]<br>{{flag|Navassa Island}}<br>{{flag|Panama}}<br>{{flag+link|Time in|Peru}}</div>
| {{TimebyUTCoffset|-|05|00}}
| style=background:#0400CD| ||<div style="column-width:20em;column-count:2">{{flag|Bahamas}}<br>{{flag+link|Time in|Canada}}: [[Time in Nunavut|Nunavut]] (east), [[Ontario]] (most), [[Quebec]] (most)<br>{{flag|Cuba}}<br>{{flag|Haiti}}<br>{{flag|Turks and Caicos Islands}}<br>{{no col break|{{flag+link|Time in|United States}}: [[Time in Connecticut|Connecticut]], [[Delaware]], [[Time in Washington, D.C.|District of Columbia]], [[Time in Florida|Florida]] (most), [[Georgia (U.S. state)|Georgia]], [[Time in Indiana|Indiana]] (most), [[Time in Kentucky|Kentucky]] (east), [[Time in Maine|Maine]], [[Maryland]], [[Time in Massachusetts|Massachusetts]], [[Time in Michigan|Michigan]] (most), [[Time in New Hampshire|New Hampshire]], [[New Jersey]], [[Time in New York|New York]], [[North Carolina]], [[Ohio]], [[Pennsylvania]], [[Time in Rhode Island|Rhode Island]], [[South Carolina]], [[Time in Tennessee|Tennessee]] (east), [[Time in Vermont|Vermont]], [[Virginia]], [[West Virginia]]}}</div>
| {{flagicon|BRA}}[[Time in Brazil|Brazil]] ([[Acre (state)|Acre]]), {{COL}}, {{ECU}} (continental), {{HAI}}, {{JAM}}, {{flagicon|MEX}}[[Time in Mexico|Mexico]] {{flagicon|Quintana Roo}} (most of [[Quintana Roo]]), {{PAN}}, {{PER}}
| {{flagicon|Bahamas}}[[Bahamas]], {{flagicon|CAN}}[[Time in Canada|Canada]] ({{flagicon|Ontario}}most of [[Ontario]], {{flagicon|QC}}most of [[Quebec]]), {{CUB}}, {{flagicon|USA}}[[Time in the United States|United States]] {{flagicon|Florida}}(most of [[Florida]], {{flagicon|Georgia (U.S. state)}}[[Georgia (U.S. state)|Georgia]], {{flagicon|New York (state)}}[[New York (state)|New York]], {{flagicon|Ohio}}[[Ohio]], {{flagicon|Pennsylvania}}[[Pennsylvania]])
|-
|-
| [[UTC−04:00]]
| [[UTC−04:00]]
| style=background:#00FF85| ||<div style="column-width:10em;column-count:2">{{flag|Anguilla}}<br>{{flag+link|Time in|Antigua and Barbuda}}<br>{{flag|Aruba}}<br>{{flag|Barbados}}<br>{{flag|Bolivia}}<br>{{flag+link|Time in|Brazil}}: [[Amazonas (Brazilian state)|Amazonas]] (most), [[Mato Grosso]], [[Mato Grosso do Sul]], [[Rondônia]], [[Roraima]]<br>{{flag|British Virgin Islands}}<br>{{flag+link|Time in|Canada}}: [[Quebec]] (east)<br>{{flag|Caribbean Netherlands}}<br>{{flag|Curaçao}}<br>{{flag|Dominica}}<br>{{no col break|{{flag|Dominican Republic}}}}{{flag|Grenada}}<br>{{flag|Guadeloupe}}<br>{{flag|Guyana}}<br>{{flag|Martinique}}<br>{{flag|Montserrat}}<br>{{flag+link|Time in|Puerto Rico}}<br>{{flag|Saint Barthélemy}}<br>{{flag|Saint Kitts and Nevis}}<br>{{flag|Saint Lucia}}<br>{{flag|Saint Martin}}<br>{{flag|Saint Vincent and the Grenadines}}<br>{{flag|Sint Maarten}}<br>{{flag+link|Time in|Trinidad and Tobago}}<br>{{flag+link|Time in|United States Virgin Islands}}<br>{{flag+link|Time in|Venezuela}}</div>
| {{TimebyUTCoffset|-|04|00}}
| style=background:#00BF63| ||{{flag|Bermuda}}<br>{{flag+link|Time in|Canada}}: [[Labrador]] (most), [[New Brunswick]], [[Nova Scotia]], [[Prince Edward Island]]<br>{{flag+link|Time in|Chile}} (most)<br>{{flag+link|Time in|Greenland}}: [[Pituffik Space Base]]
| {{BAR}}, {{BOL}}, {{flagicon|BRA}}[[Time in Brazil|Brazil]] (most of [[Amazonas (Brazilian state)|Amazonas]], {{flagicon|Rondônia}} [[Rondônia]], {{flagicon|Roraima}} [[Roraima]]), {{DOM}}, {{flagicon|Puerto Rico}} [[Puerto Rico]], {{TTO}}, {{flagicon|VEN}} [[Time in Venezuela|Venezuela]]
| {{flagicon|BRA}} [[Time in Brazil|Brazil]] ({{flagicon|Mato Grosso}} most of [[Mato Grosso]], {{flagicon|Mato Grosso do Sul}} [[Mato Grosso do Sul]]), {{flagicon|CAN}} [[Time in Canada|Canada]] ({{flagicon|Nova Scotia}} [[Nova Scotia]], {{flagicon|New Brunswick}} [[New Brunswick]] and {{flagicon|Labrador}} most of [[Labrador]], {{flagicon|Prince Edward Island}} [[Prince Edward Island]]), {{CHI}} (continental), {{PAR}}
|-
|-
| [[UTC−03:30]]
| [[UTC−03:30]]
| style=background:#A9FF13| ||
| {{TimebyUTCoffset|-|03|30}}
| style=background:#419300| ||{{flag+link|Time in|Canada}}: [[Newfoundland (island)|Newfoundland]], [[Labrador]] (southeast)
|
| {{flagicon|CAN}} [[Time in Canada|Canada]] ({{flagicon|Newfoundland and Labrador}} island of [[Newfoundland and Labrador|Newfoundland]], southeastern [[Labrador]])
|-
|-
| [[UTC−03:00]]
| [[UTC−03:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Argentina}}<br>{{flag+link|Time in|Brazil}} (most)<br>{{flag+link|Time in|Chile}}: [[Magallanes Region]]<br>{{flag+link|Time in|Falkland Islands}}<br>{{flag|French Guiana}}<br>{{flag+link|Time in|Paraguay}}<br>{{flag|Suriname}}<br>{{flag+link|Time in|Uruguay}}</div>
| {{TimebyUTCoffset|-|03|00}}
| style=background:#D3D800| ||{{flag|Saint Pierre and Miquelon}}
| {{flagicon|ARG}} [[Time in Argentina|Argentina]], {{flagicon|BRA}} [[Time in Brazil|Brazil]] ({{flagicon|Bahia}} [[Bahia]], {{flagicon|Ceará}} [[Ceará]], {{flagicon|Maranhão}} [[Maranhão]], {{flagicon|Pará}} [[Pará]], {{flagicon|Pernambuco}} [[Pernambuco]]), {{flagicon|CHI}} [[Time in Chile|Chile]] ([[Magallanes Region]]), {{flagicon|Falkland Islands}} [[Time in the Falkland Islands|Falkland Islands]], {{flagicon|Saint Pierre and Miquelon}} [[UTC−03:00|Saint Pierre and Miquelon]], {{URU}}
| {{flagicon|BRA}} [[Time in Brazil|Brazil]] ([[Federal District (Brazil)|Federal District]], {{flagicon|Minas Gerais}} [[Minas Gerais]], [[Paraná (state)|Paraná]], {{flagicon|Rio Grande do Sul}} [[Rio Grande do Sul]], [[Rio de Janeiro (state)|Rio de Janeiro]], [[São Paulo (state)|São Paulo]]), {{flagicon|Greenland}} [[Greenland]] (most)
|-
|-
| [[UTC−02:00]]
| [[UTC−02:00]]
| style=background:#FF409C| ||{{flag+link|Time in|Brazil}}: [[Fernando de Noronha]]<br>{{flag|South Georgia and the South Sandwich Islands}}
| {{TimebyUTCoffset|-|02|00}}
| style=background:#DE006A| ||{{flag+link|Time in|Greenland}} (most)
| {{flagicon|BRA}} [[Time in Brazil|Brazil]] ([[Fernando de Noronha]]), {{flagicon|South Georgia and the South Sandwich Islands}} [[South Georgia and the South Sandwich Islands]]
|
|-
|-
| [[UTC−01:00]]
| [[UTC−01:00]]
| style=background:#6D6AFF| ||{{flag+link|Time in|Cape Verde}}
| {{TimebyUTCoffset|-|01|00}}
| style=background:#0400CD| ||{{flag+link|Time in|Portugal}}: [[Azores]]
| {{CPV}}
| {{POR}} ({{flagicon|Azores}} [[Azores]])
|-
|-
| [[UTC±00:00]]
| [[UTC+00:00]]
| style=background:#00FF85| ||<div style="column-width:10em;column-count:2">{{flag|Burkina Faso}}<br>{{flag|Gambia}}<br>{{flag|Ghana}}<br>{{flag+link|Time in|Greenland}}: [[Northeast Greenland National Park|National Park]] (east coast)<br>{{flag|Guinea}}<br>{{flag|Guinea-Bissau}}<br>{{flag|Iceland}}<br>{{flag|Ivory Coast}}<br>{{flag|Liberia}}<br>{{flag|Mali}}<br>{{flag|Mauritania}}<br>{{flag|Saint Helena, Ascension and Tristan da Cunha}}<br>{{flag|Senegal}}<br>{{flag|Sierra Leone}}<br>{{flag|São Tomé and Príncipe}}<br>{{flag|Togo}}</div>
| {{TimebyUTCoffset|+|00|00}}
| style=background:#00BF63| ||{{flag+link|Time in|Faroe Islands}}<br>{{flag|Bailiwick of Guernsey|name=Guernsey}}<br>{{flag+link|Time in|Ireland}}<br>{{flag|Isle of Man}}<br>{{flag|Jersey}}<br>{{flag+link|Time in|Portugal}} (most)<br>{{flag+link|Time in|Spain}}: [[Canary Islands]]<br>{{flag+link|Time in|United Kingdom}}
| {{CIV}}, {{GHA}}, {{ISL}}, {{flagicon|Saint Helena}} [[Saint Helena, Ascension and Tristan da Cunha|Saint Helena]], {{SEN}}, {{MLI}}
| {{flagicon|Faroe Islands}} [[Faroe Islands]], {{IRL}}, {{POR}} ([[Continental Portugal|continental]], {{flagicon|Madeira}} [[Madeira]]), {{ESP}} ({{flagicon|Canary Islands}} [[Canary Islands]]), {{GBR}}
|-
|-
| [[UTC+01:00]]
| [[UTC+01:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Algeria}}<br>{{flag+link|Time in|Angola}}<br>{{flag|Benin}}<br>{{flag|Cameroon}}<br>{{flag|Central African Republic}}<br>{{flag|Chad}}<br>{{flag|Congo}}<br>{{no col break|{{flag+link|Time in|DR Congo|name=Democratic Republic of the Congo}}: [[Province of Équateur|Équateur]], [[Kinshasa]], [[Kongo Central]], [[Kwango]], [[Kwilu Province|Kwilu]], [[Mai-Ndombe Province|Mai-Ndombe]], [[Mongala]], [[Nord-Ubangi]], [[Sud-Ubangi]], [[Tshuapa]]}}{{flag|Equatorial Guinea}}<br>{{flag|Gabon}}<br>{{flag+link|Time in|Morocco}}{{efn|name=ma|Observes UTC+00:00 around [[Ramadan]].<ref>{{cite web |url=https://www.timeanddate.com/news/time/morocco-changes-clocks-2019.html |title=Morocco Re-Introduces Clock Changes for Ramadan 2019 |publisher=Timeanddate.com |date=April 19, 2019 |archive-url=https://web.archive.org/web/20201228210847/https://www.timeanddate.com/news/time/morocco-changes-clocks-2019.html |archive-date=December 28, 2020 |url-status=live}}</ref><ref>{{cite web |url=https://www.timeanddate.com/time/zone/morocco/casablanca |title=Time Zone in Casablanca, Morocco |publisher=Timeanddate.com |archive-url=https://web.archive.org/web/20210330010901/https://www.timeanddate.com/time/zone/morocco/casablanca |archive-date=March 30, 2021 |url-status=live}}</ref><ref>{{cite web |url=https://www.timeanddate.com/time/zone/western-sahara/el-aaiun |title=Time Zone in El Aaiún, Western Sahara |publisher=Timeanddate.com |archive-url=https://web.archive.org/web/20210214122434/https://www.timeanddate.com/time/zone/western-sahara/el-aaiun |archive-date=February 14, 2021 |url-status=live}}</ref>}}<br>{{flag|Niger}}<br>{{flag|Nigeria}}<br>{{flag+link|Time in|Tunisia}}<br>''{{flag|Western Sahara}}''{{efn|name=ma}}</div>
| {{TimebyUTCoffset|+|01|00}}
| style=background:#D3D800| ||<div style="column-width:10em;column-count:3">{{flag|Albania}}<br>{{flag|Andorra}}<br>{{flag|Austria}}<br>{{flag+link|Time in|Belgium}}<br>{{flag+link|Time in|Bosnia and Herzegovina}}<br>{{flag|Croatia}}<br>{{flag+link|Time in|Czech Republic}}<br>{{flag+link|Time in|Denmark}}<br>{{flag+link|Time in|France}} ([[Metropolitan France|metropolitan]])<br>{{flag+link|Time in|Germany}}<br>{{flag+link|Time in|Gibraltar}}<br>{{flag+link|Time in|Hungary}}<br>{{flag+link|Time in|Italy}}<br>''{{flag|Kosovo}}''<br>{{flag|Liechtenstein}}<br>{{flag|Luxembourg}}<br>{{flag+link|Time in|Malta}}<br>{{flag|Monaco}}<br>{{flag|Montenegro}}<br>{{flag+link|Time in|Netherlands}} (European)<br>{{flag|North Macedonia}}<br>{{flag+link|Time in|Norway}}<br>{{flag|Poland}}<br>{{flag|San Marino}}<br>{{flag|Serbia}}<br>{{flag+link|Time in|Slovakia}}<br>{{flag|Slovenia}}<br>{{flag+link|Time in|Spain}} (most)<br>{{flag|Sweden}}<br>{{flag+link|Time in|Switzerland}}<br>{{flag|Vatican City}}</div>
| {{ALG}}, {{ANG}}, {{BEN}}, {{CMR}}, {{COD}} (west), {{GAB}}, {{MAR}}, {{NIG}}, {{NGR}}, {{TUN}}, {{flag|Western Sahara}}
| {{ALB}}, {{AUT}}, {{BEL}}, {{BIH}}, {{CRO}}, {{CZE}}, {{DEN}}, {{FRA}} ([[Metropolitan France|metropolitan]]), {{flagicon|GER}} [[Time in Germany|Germany]], {{HUN}}, {{ITA}}, {{MLT}}, {{MKD}}, {{NED}} (European), {{NOR}}, {{POL}}, {{SRB}}, {{SVK}}, {{SLO}}, {{ESP}} (continental), {{SWE}}, {{SUI}}
|-
|-
| [[UTC+02:00]]
| [[UTC+02:00]]
| style=background:#FF409C| ||<div style="column-width:10em;column-count:2">{{flag|Botswana}}<br>{{flag|Burundi}}<br>{{flag+link|Time in|DR Congo|name=Democratic Republic of the Congo}} (most)<br>{{flag|Eswatini}}<br>{{flag|Lesotho}}<br>{{flag|Libya}}<br>{{flag|Malawi}}<br>{{flag|Mozambique}}<br>{{flag+link|Time in|Namibia}}<br>{{flag+link|Time in|Russia}}: [[Kaliningrad Oblast|Kaliningrad]]<br>{{flag|Rwanda}}<br>{{flag+link|Time in|South Africa}} (most)<br>{{flag|South Sudan}}<br>{{flag|Sudan}}<br>{{flag|Zambia}}<br>{{flag|Zimbabwe}}</div>
| {{TimebyUTCoffset|+|02|00}}
| style=background:#DE006A| ||<div style="column-width:10em;column-count:3">{{flag|Akrotiri and Dhekelia}}<br>{{flag|Bulgaria}}<br>{{flag+link|Time in|Cyprus}}<br>{{flag+link|Time in|Egypt}}<br>{{flag+link|Time in|Estonia}}<br>{{flag+link|Time in|Finland}}<br>{{flag|Greece}}<br>{{flag+link|Time in|Israel}}<br>{{flag|Latvia}}<br>{{flag+link|Time in|Lebanon}}<br>{{flag+link|Time in|Lithuania}}<br>{{flag|Moldova}}<br>''{{flag|Northern Cyprus}}''<br>{{flag+link|Time in|Palestine}}<br>{{flag|Romania}}<br>''{{flag|Transnistria}}''<br>{{flag+link|Time in|Ukraine}} (most)</div>
| {{BDI}}, {{EGY}}, {{MAW}}, {{MOZ}}, {{NAM}}, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Kaliningrad Oblast}} [[Kaliningrad Oblast|Kaliningrad]]), {{RWA}}, {{RSA}}, {{SUD}}, {{SWZ}}, {{ZAM}}, {{ZIM}}
| {{BUL}}, {{CYP}}, {{EST}}, {{FIN}}, {{GRE}}, {{ISR}}, {{JOR}}, {{LAT}}, {{LBN}}, {{LIT}}, {{MDA}}, {{flagicon|Palestine}} [[State of Palestine|Palestine]], {{ROM}}, {{SYR}}, {{UKR}}
|-
|-
| [[UTC+03:00]]
| [[UTC+03:00]]
| style=background:#6D6AFF| ||<div style="column-width:10em;column-count:2">''{{flag|Abkhazia}}''<br>{{flag+link|Time in|Bahrain}}<br>{{flag+link|Time in|Belarus}}<br>{{flag|Comoros}}<br>{{flag|Djibouti}}<br>{{flag|Eritrea}}<br>{{flag+link|Time in|Ethiopia}}<br>{{flag|French Southern and Antarctic Lands}}: [[Scattered Islands]]<ref name=fr>{{cite web |url=https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000034154759 |title=Décret nº 2017-292 du 6 mars 2017 relatif au temps légal français |trans-title=Decree no. 2017-292 of 6 March 2017 relative to French legal time |publisher=Légifrance |date=March 8, 2017 |language=fr |archive-url=https://web.archive.org/web/20201202160854/https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000034154759/ |archive-date=December 2, 2020 |url-status=live}}</ref><br>{{flag+link|Time in|Iraq}}<br>{{flag+link|Time in|Jordan}}<br>{{flag+link|Time in|Kenya}}<br>{{flag+link|Time in|Kuwait}}<br>{{flag|Madagascar}}<br>{{flag|Mayotte}}<br>{{flag+link|Time in|Qatar}}<br>{{flag+link|Time in|Russia}} (most of [[European Russia|European part]])<br>{{flag+link|Time in|Saudi Arabia}}<br>{{flag|Somalia}}<br>''{{flag|Somaliland}}''<br>{{flag+link|Time in|South Africa}}: [[Prince Edward Islands]]<br>''{{flag+link|Time in|South Ossetia}}''<br>{{flag+link|Time in|Syria}}<br>{{flag|Tanzania}}<br>{{flag+link|Time in|Turkey}}<br>{{flag|Uganda}}<br>{{flag|Ukraine}}: [[Russian-occupied territories of Ukraine|occupied territories]]<br>{{flag+link|Time in|Yemen}}</div>
| {{TimebyUTCoffset|+|03|00}}
| style=background:#0400CD| ||
| {{BLR}}, {{DJI}}, {{ERI}}, {{ETH}}, {{IRQ}}, {{KEN}}, {{KUW}}, {{MAD}}, {{flagicon|RUS}} [[Time in Russia|Russia]] (most of [[European Russia|European part]]), {{KSA}}, {{QAT}}, {{SOM}}, {{SSD}}, {{TAN}}, {{TUR}}, {{UGA}}, {{YEM}},
|
|-
|-
| [[UTC+03:30]]
| [[UTC+03:30]]
| style=background:#35C8FF| ||{{flag+link|Time in|Iran}}
| {{TimebyUTCoffset|+|03|30}}
| style=background:#0080B2| ||
|
| {{IRI}}
|-
|-
| [[UTC+04:00]]
| [[UTC+04:00]]
| style=background:#00FF85| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Armenia}}<br>{{flag+link|Time in|Azerbaijan}}<br>{{flag|French Southern and Antarctic Lands}}: [[Crozet Islands]]<ref name=fr/><br>{{flag+link|Time in|Georgia}}<br>{{flag+link|Time in|Mauritius}}<br>{{flag+link|Time in|Oman}}<br>{{flag+link|Time in|Russia}}: [[Astrakhan Oblast|Astrakhan]], [[Samara Oblast|Samara]], [[Saratov Oblast|Saratov]], [[Udmurtia]], [[Ulyanovsk Oblast|Ulyanovsk]]<br>{{flag|Réunion}}<br>{{flag|Seychelles}}<br>{{flag+link|Time in|United Arab Emirates}}</div>
| {{TimebyUTCoffset|+|04|00}}
| style=background:#00BF63| ||
| {{ARM}}, {{AZE}}, {{GEO}}, {{MRI}}, {{OMA}}, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Samara Oblast}} [[Samara Oblast|Samara]]), {{SEY}}, {{UAE}}
|
|-
|-
| [[UTC+04:30]]
| [[UTC+04:30]]
| style=background:#A9FF13| ||{{flag+link|Time in|Afghanistan}}
| {{TimebyUTCoffset|+|04|30}}
| style=background:#419300| ||
| {{AFG}}
|
|-
|-
| [[UTC+05:00]]
| [[UTC+05:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag|French Southern and Antarctic Lands}}: [[Kerguelen Islands]], [[Île Saint-Paul|Saint Paul Island]], [[Île Amsterdam|Amsterdam Island]]<br>{{flag|Heard Island and McDonald Islands}}<br>{{flag+link|Time in|Kazakhstan}}<br>{{flag+link|Time in|Maldives}}<br>{{flag+link|Time in|Pakistan}}<br>{{flag+link|Time in|Russia}}: [[Bashkortostan]], [[Chelyabinsk Oblast|Chelyabinsk]], [[Khanty-Mansi Autonomous Okrug|Khanty-Mansi]], [[Kurgan Oblast|Kurgan]], [[Orenburg Oblast|Orenburg]], [[Perm Krai|Perm]], [[Sverdlovsk Oblast|Sverdlovsk]], [[Tyumen Oblast|Tyumen]], [[Yamalia]]<br>{{flag+link|Time in|Tajikistan}}<br>{{flag+link|Time in|Turkmenistan}}<br>{{flag+link|Time in|Uzbekistan}}</div>
| {{TimebyUTCoffset|+|05|00}}
| style=background:#D3D800| ||
| {{KAZ}} (west), {{MDV}}, {{PAK}}, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Sverdlovsk Oblast}} [[Sverdlovsk Oblast|Sverdlovsk]], {{flagicon|Chelyabinsk Oblast}} [[Chelyabinsk Oblast|Chelyabinsk]]), {{UZB}}
|
|-
|-
| [[UTC+05:30]]
| [[UTC+05:30]]
| style=background:#FF9F25| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|India}}<br>{{flag+link|Time in|Sri Lanka}}</div>
| {{TimebyUTCoffset|+|05|30}}
| style=background:#F05F00| ||
| {{IND}}, {{SRI}}
|
|-
|-
| [[UTC+05:45]]
| [[UTC+05:45]]
| style=background:#FF2F2F| ||{{flag+link|Time in|Nepal}}
| {{TimebyUTCoffset|+|05|45}}
| style=background:#D0D0D0| ||
| {{NEP}}
|
|-
|-
| [[UTC+06:00]]
| [[UTC+06:00]]
| style=background:#FF409C| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Bangladesh}}<br>{{flag+link|Time in|Bhutan}}<br>{{flag|British Indian Ocean Territory}}<br>{{flag+link|Time in|Kyrgyzstan}}<br>{{flag+link|Time in|Russia}}: [[Omsk Oblast|Omsk]]</div>
| {{TimebyUTCoffset|+|06|00}}
| style=background:#DE006A| ||
| {{BAN}}, {{flagicon|Bhutan}} [[Bhutan]], {{flagicon|British Indian Ocean Territory}} [[British Indian Ocean Territory]], {{KAZ}} (most), {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Omsk Oblast}} [[Omsk Oblast|Omsk]])
|
|-
|-
| [[UTC+06:30]]
| [[UTC+06:30]]
| style=background:#CD61FF| ||<div style="column-width:10em;column-count:2">{{flag|Cocos (Keeling) Islands}}<br>{{flag+link|Time in|Myanmar}}</div>
| {{TimebyUTCoffset|+|06|30}}
| style=background:#9900E0| ||
| {{flagicon|Cocos Islands}} [[Cocos Islands]], {{MYA}}
|
|-
|-
| [[UTC+07:00]]
| [[UTC+07:00]]
| style=background:#6D6AFF| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Cambodia}}<br>{{flag|Christmas Island}}<br>{{flag+link|Time in|Indonesia}}: [[Sumatra]], [[Java]], [[West Kalimantan]], [[Central Kalimantan]]<br>{{flag+link|Time in|Laos}}<br>{{no col break|{{flag+link|Time in|Mongolia}}: [[Bayan-Ölgii Province|Bayan-Ölgii]], [[Khovd Province|Khovd]], [[Uvs Province|Uvs]]}}{{flag+link|Time in|Russia}}: [[Altai Krai]], [[Altai Republic]], [[Kemerovo Oblast|Kemerovo]], [[Khakassia]], [[Krasnoyarsk Krai|Krasnoyarsk]], [[Novosibirsk Oblast|Novosibirsk]], [[Tomsk Oblast|Tomsk]], [[Tuva]]<br>{{flag+link|Time in|Thailand}}<br>{{flag+link|Time in|Vietnam}}</div>
| {{TimebyUTCoffset|+|07|00}}
| style=background:#0400CD| ||
| {{CAM}}, {{INA}} (west), {{LAO}}, {{flagicon|MGL}} [[Time in Mongolia|Mongolia]] (west), {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Krasnoyarsk Krai}} [[Krasnoyarsk Krai|Krasnoyarsk]]), {{THA}}, {{VIE}}
|
|-
|-
| [[UTC+08:00]]
| [[UTC+08:00]]
| style=background:#00FF85| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Australia}}: [[Western Australia]] (most)<br>{{flag+link|Time in|Brunei}}<br>{{flag+link|Time in|China}}<br>{{flag+link|Time in|Hong Kong}}<br>{{no col break|{{flag+link|Time in|Indonesia}}: [[South Kalimantan]], [[East Kalimantan]], [[North Kalimantan]], [[Sulawesi]], [[Lesser Sunda Islands]]}}{{flag+link|Time in|Macau}}<br>{{flag+link|Time in|Malaysia}}<br>{{flag+link|Time in|Mongolia}} (most)<br>{{flag+link|Time in|Philippines}}<br>{{flag+link|Time in|Russia}}: [[Buryatia]], [[Irkutsk Oblast|Irkutsk]]<br>{{flag+link|Time in|Singapore}}<br>''{{flag+link|Time in|Taiwan}}''</div>
| {{TimebyUTCoffset|+|08|00}}
| style=background:#00BF63| ||
| {{flagicon|AUS}} [[Time in Australia|Australia]] ({{flagicon|Western Australia}} [[Western Australia]]), {{flagicon|Brunei}} [[Brunei]], {{PRC}}, {{HKG}}, {{INA}} (central), {{MAC}}, {{MAS}}, {{flagicon|MGL}} [[Time in Mongolia|Mongolia]] (most), {{PHI}}, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Irkutsk Oblast}} [[Irkutsk Oblast|Irkutsk]]), {{SIN}}, {{ROC}}
|
|-
|-
| [[UTC+08:45]]
| [[UTC+08:45]]
| style=background:#A5FB00| ||{{flag+link|Time in|Australia}}: [[Eucla, Western Australia|Eucla]]
| {{TimebyUTCoffset|+|08|45}}
| style=background:#8ED800| ||
| {{AUS}} ([[Eucla]] unofficial)
|
|-
|-
| [[UTC+09:00]]
| [[UTC+09:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|East Timor}}<br>{{flag+link|Time in|Indonesia}}: [[Maluku Islands]], [[Western New Guinea]]<br>{{flag+link|Time in|Japan}}<br>{{flag+link|Time in|North Korea}}<br>{{flag|Palau}}<br>{{flag+link|Time in|Russia}}: [[Amur Oblast|Amur]], [[Sakha Republic|Sakha]] (most), [[Zabaykalsky Krai|Zabaykalsky]]<br>{{flag+link|Time in|South Korea}}</div>
| {{TimebyUTCoffset|+|09|00}}
| style=background:#D3D800| ||
| {{TLS}}, {{INA}} (east), {{JPN}}, {{PRK}}<ref>{{cite news | date = May 4, 2018 | last1 = Taylor | first1 = Adam | title = The brief history of North Korea's time zone | work = Washington Post | url = https://www.washingtonpost.com/news/worldviews/wp/2018/05/04/the-brief-history-of-north-koreas-time-zone/}}</ref>, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Sakha Republic}} most of [[Sakha Republic|Sakha]]), {{KOR}}
|
|-
|-
| [[UTC+09:30]]
| [[UTC+09:30]]
| style=background:#FF9F25| ||{{flag+link|Time in|Australia}}: [[Northern Territory]]
| {{TimebyUTCoffset|+|09|30}}
| style=background:#F05F00| ||{{flag+link|Time in|Australia}}: [[South Australia]], [[Yancowinna County]]<ref>{{cite web |title=Standard Time Act 1987 No 149 |url=https://legislation.nsw.gov.au/view/whole/html/inforce/current/act-1987-149 |publisher=New South Wales Government |access-date=February 29, 2024}}</ref>
| {{flagicon|AUS}} [[Time in Australia|Australia]] ({{flagicon|Northern Territory}} [[Northern Territory]])
| {{flagicon|AUS}} [[Time in Australia|Australia]] ({{flagicon|South Australia}} [[South Australia]])
|-
|-
| [[UTC+10:00]]
| [[UTC+10:00]]
| style=background:#FF409C| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Australia}}: [[Queensland]]<br>{{flag+link|Time in|Guam}}<br>{{flag|Micronesia}}: [[Chuuk State|Chuuk]], [[Yap State|Yap]]<br>{{no col break|{{flag+link|Time in|Northern Mariana Islands}}}}{{no col break|{{flag|Papua New Guinea}} (most)}}{{flag+link|Time in|Russia}}: [[Jewish Autonomous Oblast|Jewish]], [[Khabarovsk Krai|Khabarovsk]], [[Primorsky Krai|Primorsky]], [[Sakha Republic|Sakha]] (central-east)</div>
| {{TimebyUTCoffset|+|10|00}}
| style=background:#DE006A| ||{{flag+link|Time in|Australia}}: [[Australian Capital Territory]], [[Jervis Bay Territory]], [[New South Wales]] (most), [[Tasmania]], [[Victoria (Australia)|Victoria]]
| {{flagicon|AUS}} [[Time in Australia|Australia]] ({{flagicon|Queensland}} [[Queensland]]), {{PNG}}, {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Primorsky Krai}} [[Primorsky Krai|Primorsky]])
| {{flagicon|AUS}} [[Time in Australia|Australia]] ({{flagicon|New South Wales}} [[New South Wales]], {{flagicon|Tasmania}} [[Tasmania]], {{flagicon|Victoria}} [[Victoria (Australia)|Victoria]])
|-
|-
| [[UTC+10:30]]
| [[UTC+10:30]]
| style=background:#CD61FF| ||
| {{TimebyUTCoffset|+|10|30}}
| style=background:#9900E0| ||{{flag+link|Time in|Australia}}: [[Lord Howe Island]] (DST increase is 30 minutes)
|
| {{flagicon|Lord Howe Island}} [[Lord Howe Island]]
|-
|-
| [[UTC+11:00]]
| [[UTC+11:00]]
| style=background:#6D6AFF| ||<div style="column-width:10em;column-count:2">{{flag|Micronesia}}: [[Kosrae]], [[Pohnpei State|Pohnpei]]<br>{{flag|New Caledonia}}<br>{{no col break|{{flag|Papua New Guinea}}: [[Autonomous Region of Bougainville|Bougainville]]}}{{flag+link|Time in|Russia}}: [[Magadan Oblast|Magadan]], [[Sakha Republic|Sakha]] (east), [[Sakhalin Oblast|Sakhalin]]<br>{{flag|Solomon Islands}}<br>{{flag+link|Time in|Vanuatu}}</div>
| {{TimebyUTCoffset|+|11|00}}
| style=background:#0400CD| ||{{flag+link|Time in|Norfolk Island}}
| {{flagicon|New Caledonia}} [[New Caledonia]], {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Magadan Oblast}} [[Magadan Oblast|Magadan]]), {{SOL}}, {{VAN}}
|
|-
|-
| [[UTC+12:00]]
| [[UTC+12:00]]
| style=background:#00FF85| ||<div style="column-width:10em;column-count:2">{{flag+link|Time in|Fiji}}<br>{{flag|Kiribati}}: [[Gilbert Islands]]<br>{{flag|Marshall Islands}}<br>{{flag|Nauru}}<br>{{no col break|{{flag+link|Time in|Russia}}: [[Chukotka Autonomous Okrug|Chukotka]], [[Kamchatka Krai|Kamchatka]]}}{{flag+link|Time in|Tuvalu}}<br>{{flag|Wake Island}}<br>{{flag|Wallis and Futuna}}</div>
| {{TimebyUTCoffset|+|12|00}}
| style=background:#00BF63| ||{{flag+link|Time in|New Zealand}} (most)
| {{KIR}} ([[Gilbert Islands]]), {{flagicon|RUS}} [[Time in Russia|Russia]] ({{flagicon|Kamchatka Krai}} [[Kamchatka Krai|Kamchatka]])
| {{FIJ}}, {{flagicon|NZL}} [[Time in New Zealand|New Zealand]] (most)
|-
|-
| [[UTC+12:45]]
| [[UTC+12:45]]
| style=background:#A5FB00| ||
| {{TimebyUTCoffset|+|12|45}}
| style=background:#8ED800| ||{{flag+link|Time in|New Zealand}}: [[Chatham Islands]]
|
| {{flagicon|NZL}} [[Time in New Zealand|New Zealand]] ([[Chatham Islands]])
|-
|-
| [[UTC+13:00]]
| [[UTC+13:00]]
| style=background:#F0FF00| ||<div style="column-width:10em;column-count:2">{{flag|Kiribati}}: [[Phoenix Islands]]<br>{{flag+link|Time in|Samoa}}<br>{{flag+link|Time in|Tokelau}}<br>{{flag+link|Time in|Tonga}}</div>
| {{TimebyUTCoffset|+|13|00}}
| style=background:#D3D800| ||
| {{KIR}} ([[Phoenix Islands]]), {{flagicon|Tokelau}} [[Tokelau]], {{TON}}
| {{SAM}}
|-
|-
| [[UTC+14:00]]
| [[UTC+14:00]]
| style=background:#FF409C| ||{{flag|Kiribati}}: [[Line Islands]]
| {{TimebyUTCoffset|+|14|00}}
| style=background:#DE006A| ||
| {{KIR}} ([[Line Islands]])
|
|}
|}


== History ==
Where the adjustment for time zones results in a time at the other side of midnight from UTC, then the date at the location is one day later or earlier.
[[File:World time clock (multiple faces) 2.5m high.made in Dresden 1690, Technical Instrument Museum, Dresden.jpg|thumb|World time clock, 2.5&nbsp;m high. Made in [[Dresden]] 1690. Technical Instrument Museum, Dresden]]
The apparent position of the Sun in the sky, and thus [[solar time]], varies by location due to the [[spherical]] shape of the Earth. This variation corresponds to four [[minute]]s of time for every [[Degree (angle)|degree]] of [[longitude]], so for example when it is solar noon in [[London]], it is about 10 minutes before solar noon in [[Bristol]], which is about 2.5 degrees to the west.<ref>{{cite web |title=Latitude and Longitude of World Cities |url=http://www.infoplease.com/ipa/A0001769.html |publisher=Infoplease |access-date=April 18, 2012 |archive-date=May 24, 2011 |archive-url=https://web.archive.org/web/20110524213744/http://www.infoplease.com/ipa/A0001769.html |url-status=live }}</ref>


The [[Royal Observatory, Greenwich]], founded in 1675, established [[Greenwich Mean Time]] (GMT), the mean solar time at that location, as an aid to mariners to determine longitude at sea, providing a standard reference time while each location in [[England]] kept a different time.
Some examples when UTC is 23:00 on Monday when or where daylight saving time is not in effect:
* [[Cairo]], [[Egypt]]: [[UTC+02]]; 01:00 on Tuesday
* [[Wellington]], [[New Zealand]]: [[UTC+12]]; 11:00 on Tuesday


=== Railway time ===
Some examples when UTC is 02:00 on Tuesday when or where daylight saving time is not in effect:
{{Main|Railway time}}
* Honolulu, Hawaii, United States: [[UTC−10]]; 16:00 on Monday
[[File:Time zone chicago.jpg|thumb|right|upright|Plaque commemorating the Railway General Time Convention of 1883 in North America]]
* Toronto, Ontario, Canada: UTC−05; 21:00 on Monday
[[File:Coventry Time Zone Clock.jpg|thumb|right|The control panel of the Time Zone Clock in front of [[Coventry Transport Museum]]]]


In the 19th century, as transportation and telecommunications improved, it became increasingly inconvenient for each location to observe its own solar time. In November 1840, the British [[Great Western Railway]] started using GMT kept by portable [[marine chronometer|chronometers]].<ref>{{Cite journal|date=December 1840|title=WESTMINSTER MEDICAL SOCIETY. Saturday, November 21, 1840.|url=http://dx.doi.org/10.1016/s0140-6736(00)59842-0|journal=The Lancet|volume=35|issue=901|pages=383|doi=10.1016/s0140-6736(00)59842-0|issn=0140-6736|access-date=January 27, 2021|archive-date=March 30, 2021|archive-url=https://web.archive.org/web/20210330010908/https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(00)59842-0/fulltext|url-status=live}}</ref>{{Failed verification|date=June 2023}} This practice was soon followed by other [[History of rail transport in Great Britain|railway companies in Great Britain]] and became known as [[railway time]].
The time-zone adjustment for a specific location may vary because of daylight saving time. For example, New Zealand, which is usually [[UTC+12]], observes a one-hour daylight saving time adjustment during the [[Southern Hemisphere]] summer, resulting in a local time of [[UTC+13]].


Around August 23, 1852, time signals were first transmitted by [[telegraph]] from the Royal Observatory. By 1855, 98% of Great Britain's public clocks were using GMT, but it was not made the island's legal time until August 2, 1880. Some British clocks from this period have two minute hands, one for the local time and one for GMT.<ref>{{cite web |url=http://wwp.greenwichmeantime.com/info/bristol-time.htm |title=Bristol Time |work=GreenwichMeanTime.com |access-date=December 5, 2011 |archive-url=https://web.archive.org/web/20060628151049/http://wwp.greenwichmeantime.com/info/bristol-time.htm |archive-date=June 28, 2006 |url-status=dead }}</ref>
==Differences between cities==

From [[New York City|New York]] to other cities:
On November 2, 1868, the British [[Colony of New Zealand]] officially adopted a standard time to be observed throughout the colony.<ref>{{cite web|title=Telegraph line laid across Cook Strait.|url=https://nzhistory.govt.nz/page/submarine-telegraph-line-laid-across-cook-strait|publisher=New Zealand Ministry for Culture and Heritage|access-date=January 5, 2020|archive-date=February 18, 2020|archive-url=https://web.archive.org/web/20200218115412/https://nzhistory.govt.nz/page/submarine-telegraph-line-laid-across-cook-strait|url-status=live}}</ref> It was based on longitude {{nowrap|172°30′}} east of [[Greenwich]], that is 11 hours 30 minutes ahead of GMT. This standard was known as [[Time in New Zealand|New Zealand Mean Time]].<ref>{{cite web|title=Our Time. How we got it. New Zealand's Method. A Lead to the World.|url=http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19290408.2.88&srpos=2|work=Papers Past|publisher=Evening Post|access-date=October 2, 2013|page=10|archive-date=October 8, 2013|archive-url=https://web.archive.org/web/20131008192904/http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&cl=search&d=EP19290408.2.88&srpos=2|url-status=live}}</ref>
{| class="wikitable"
[[File:Time zone map of the United States 1913 (colorized).png|thumb|center|upright=1.6|1913 time zone map of the United States, showing boundaries very different from today]]
! Time of Day || City name

|- valign="top"
Timekeeping on [[North America]]n [[Rail transport|railroads]] in the 19th century was complex. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time. Some junctions served by several railroads had a clock for each railroad, each showing a different time.<ref>{{Cite magazine |url=https://www.wired.com/2010/11/1118railroad-time-zones/ |title=Nov. 18, 1883: Railroad Time Goes Coast to Coast |last=Alfred |first=Randy |date=November 18, 2010 |magazine=Wired |language=en-US |access-date=July 30, 2018 |archive-date=August 19, 2018 |archive-url=https://web.archive.org/web/20180819071241/https://www.wired.com/2010/11/1118railroad-time-zones/ |url-status=live }}</ref> Because of this a number of accidents occurred when trains from different companies using the same tracks mistimed their passings.<ref>{{cite web |url=https://news.harvard.edu/gazette/story/2011/11/americas-first-time-zone/ |title=America's first time zone|date=November 10, 2011 }}</ref>
| {{time|UTC-05:00|df=y}} || [[New York City|New York]]

|- valign="top" style="border-top:hidden;"
Around 1863, [[Charles F. Dowd]] proposed a system of hourly standard time zones for North American railroads, although he published nothing on the matter at that time and did not consult railroad officials until 1869. In 1870 he proposed four ideal time zones having north–south borders, the first centered on [[Washington, D.C.]], but by 1872 the first was centered on meridian [[75th meridian west|75° west of Greenwich]], with natural borders such as sections of the [[Appalachian Mountains]]. Dowd's system was never accepted by North American railroads.
| {{time|UTC±00:00|df=y}} || [[London]]
Chief meteorologist at the [[United States Weather Bureau]] [[Cleveland Abbe]] divided the United States into four standard time zones for consistency among the weather stations. In 1879, he published a paper titled ''Report on Standard Time''.<ref name=wws>{{harvnb|Debus|1968|p=2}}</ref> In 1883, he convinced North American railroad companies to adopt his time-zone system. In 1884, Britain, which had already adopted its own standard time system for England, Scotland, and Wales, helped gather international consent for global time. In time, the American government, influenced in part by Abbe's 1879 paper, adopted the time-zone system.<ref>{{harvnb|Asimov|1964|p=344}}</ref>
|}
It was a version proposed by William F. Allen, the editor of the ''Traveler's Official Railway Guide''.<ref>{{cite web |url= http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |title= Economics of Time Zones |url-status= dead |archive-url= https://web.archive.org/web/20120514014456/http://bpp.wharton.upenn.edu/mawhite/Papers/TimeZones.pdf |archive-date= May 14, 2012 }} &nbsp;{{small|(1.89&nbsp;MB)}}</ref> The borders of its time zones ran through railroad stations, often in major cities. For example, the border between its Eastern and Central time zones ran through [[Detroit]], [[Buffalo, New York|Buffalo]], [[Pittsburgh]], [[Atlanta]], and [[Charleston, South Carolina|Charleston]]. It was inaugurated on Sunday, November 18, 1883, also called "The Day of Two Noons",<ref>{{cite web |url=http://historymatters.gmu.edu/d/5748 |title=The ''Times'' Reports on "the Day of Two Noons" |work=History Matters |access-date=December 5, 2011 |archive-date=April 4, 2012 |archive-url=https://web.archive.org/web/20120404083446/http://historymatters.gmu.edu/d/5748 |url-status=live }}</ref> when each railroad station clock was reset as standard-time noon was reached within each time zone.
{| class="wikitable"

! Time of Day || City name
The North American zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within a year 85% of all cities with populations over 10,000 (about 200 cities) were using standard time.<ref>{{cite web|url=http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |title=Resolution concerning new standard time by Chicago |publisher=Sos.state.il.us |access-date=December 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111005050317/http://www.sos.state.il.us/departments/archives/from_the_ashes/doc24.html |archive-date=October 5, 2011 }}</ref> A notable exception was Detroit (located about halfway between the meridians of Eastern and Central time), which kept local time until 1900, then tried Central Standard Time, [[local mean time]], and [[Eastern Time Zone|Eastern Standard Time]] (EST) before a May 1915 ordinance settled on EST and was ratified by popular vote in August 1916. The confusion of times came to an end when standard time zones were formally adopted by the [[United States Congress|U.S. Congress]] in the [[Standard Time Act]] of March 19, 1918.
|- valign="top"

| {{time|UTC-05:00|df=y}} || [[New York City|New York]]
=== Worldwide time zones ===
|- valign="top" style="border-top:hidden;"
{{Redirect|World time|the global time standard|Universal Time}}
| {{time|UTC+01:00|df=y}} || [[Berlin]]
[[Italy|Italian]] mathematician [[Quirico Filopanti]] introduced the idea of a worldwide system of time zones in his book ''Miranda!'', published in 1858. He proposed 24 hourly time zones, which he called "longitudinal days", the first centred on the meridian of [[Rome]]. He also proposed a universal time to be used in astronomy and telegraphy. However, his book attracted no attention until long after his death.<ref>{{cite web |url=http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html |title=Quirico Filopanti from scienzagiovane, Bologna University, Italy |archive-url=https://web.archive.org/web/20130117011106/http://www.scienzagiovane.unibo.it/english/scientists/filopanti-1.html |archive-date=January 17, 2013 |url-status=dead}}</ref><ref>{{cite web |title=Suggestions from... ...Gianluigi Parmeggiani, Osservatorio Astronomico di Bologna - The origin of time zones |url=http://www.iav.it/planetario/didastro/didastro/english.htm |archive-url=https://web.archive.org/web/20070824155341/http://www.iav.it/planetario/didastro/didastro/english.htm |archive-date=August 24, 2007 |url-status=dead}}</ref>
|}

{| class="wikitable"
[[Scotland|Scottish]]-born [[Canada|Canadian]] Sir [[Sandford Fleming]] proposed a worldwide system of time zones in 1876 - see {{section link|Sandford Fleming|Inventor of worldwide standard time}}. The proposal divided the world into twenty-four time zones labeled A-Y (skipping J), each one covering 15 degrees of longitude. All clocks within each zone would be set to the same time as the others, but differed by one hour from those in the neighboring zones.<ref>{{Cite journal| issue = 1| pages = 345–366| last = Fleming| first = Sandford| title = Time-reckoning for the twentieth century| journal = Annual Report of the Board of Regents of the Smithsonian Institution| date = 1886| url = https://library.si.edu/digital-library/book/annualreportofbo18861smit| access-date = March 24, 2022| archive-date = October 5, 2022| archive-url = https://web.archive.org/web/20221005110429/https://library.si.edu/digital-library/book/annualreportofbo18861smit| url-status = live}} Reprinted in 1889: {{Internet Archive|timereckoningfor00flem|''Time-reckoning for the twentieth century''}}.</ref> He advocated his system at several international conferences, including the [[International Meridian Conference]], where it received some consideration. The system has not been directly adopted, but some maps divide the world into 24 time zones and assign letters to them, similarly to Fleming's system.<ref>{{cite news |last1=Stromberg |first1=Joseph |title=Sandford Fleming Sets the World's Clock |url=https://www.smithsonianmag.com/smithsonian-institution/sandford-fleming-sets-the-worlds-clock-389930/ |work=Smithsonian Magazine |date=November 18, 2011 |language=en |access-date=March 24, 2022 |archive-date=March 24, 2022 |archive-url=https://web.archive.org/web/20220324012426/https://www.smithsonianmag.com/smithsonian-institution/sandford-fleming-sets-the-worlds-clock-389930/ |url-status=live }}</ref>
! Time of Day || City name

|- valign="top"
[[File:World Time Zone Chart 1942.jpg|thumb|400px|World map of time zones in 1928]]
| {{time|UTC-05:00|df=y}} || [[New York City|New York]]

|- valign="top" style="border-top:hidden;"
By about 1900, almost all inhabited places on Earth had adopted a standard time zone, but only some of them used an hourly offset from GMT. Many applied the time at a local astronomical observatory to an entire country, without any reference to GMT. It took many decades before all time zones were based on some standard offset from GMT or [[Coordinated Universal Time]] (UTC). By 1929, the majority of countries had adopted hourly time zones, though some countries such as [[Iran]], [[India]], [[Myanmar]] and parts of [[Australia]] had time zones with a 30-minute offset. [[Nepal]] was the last country to adopt a standard offset, shifting slightly to UTC+05:45 in 1986.<ref>{{Cite web|title=Time Zone & Clock Changes in Kathmandu, Nepal|url=https://www.timeanddate.com/time/zone/nepal/kathmandu|access-date=December 1, 2020|website=timeanddate.com|language=en|archive-date=January 22, 2021|archive-url=https://web.archive.org/web/20210122042454/https://www.timeanddate.com/time/zone/nepal/kathmandu|url-status=live}}</ref>
| {{time|UTC+03:00|df=y}} || [[Moscow]]

|}
All nations currently use standard time zones for secular purposes, but not all of them apply the concept as originally conceived. Several countries and subdivisions use half-hour or quarter-hour deviations from standard time. Some countries, such as [[China]] and [[India]], use a single time zone even though the extent of their territory far exceeds the ideal 15° of longitude for one hour; other countries, such as [[Spain]] and [[Argentina]], use standard hour-based offsets, but not necessarily those that would be determined by their geographical location. The consequences, in some areas, can affect the lives of local citizens, and in extreme cases contribute to larger political issues, such as in the western reaches of China.<ref>{{Cite news|url=https://www.theatlantic.com/china/archive/2013/11/china-only-has-one-time-zone-and-thats-a-problem/281136/|title=China Only Has One Time Zone—and That's a Problem|last=Schiavenza|first=Matt|date=November 5, 2013|work=The Atlantic|access-date=August 22, 2018|language=en-US|archive-date=August 22, 2018|archive-url=https://web.archive.org/web/20180822145736/https://www.theatlantic.com/china/archive/2013/11/china-only-has-one-time-zone-and-thats-a-problem/281136/|url-status=live}}</ref> In [[Time in Russia|Russia, which has 11 time zones]], two time zones were removed in 2010<ref>{{cite web|url=https://www.timeanddate.com/news/time/russia-reduces-time-zones.html|title=Russia Reduces Number of Time Zones|date=March 23, 2010|work=TimeAndDate.com|access-date=May 31, 2020|archive-date=August 9, 2020|archive-url=https://web.archive.org/web/20200809084135/https://www.timeanddate.com/news/time/russia-reduces-time-zones.html|url-status=live}}</ref><ref>{{cite web|title=About Time: Huge country, nine time zones|date=March 22, 2011|access-date=February 12, 2019|format=Video|website=[[BBC]]|language=en|url=https://www.bbc.com/news/av/world-europe-12809230/about-time-huge-country-nine-time-zones|archive-date=February 13, 2019|archive-url=https://web.archive.org/web/20190213012708/https://www.bbc.com/news/av/world-europe-12809230/about-time-huge-country-nine-time-zones|url-status=live}}</ref> and reinstated in 2014.<ref>{{cite news |title=Russian clocks to retreat again in winter, 11 time zones return |url=https://uk.reuters.com/article/us-russia-time/russian-clocks-to-retreat-again-in-winter-11-time-zones-return-idUSKBN0F64YB20140701 |website=Reuters |date=July 2014 |access-date=October 25, 2020 |archive-date=October 28, 2020 |archive-url=https://web.archive.org/web/20201028205217/https://uk.reuters.com/article/us-russia-time/russian-clocks-to-retreat-again-in-winter-11-time-zones-return-idUSKBN0F64YB20140701 |url-status=dead }}</ref>
{| class="wikitable"

! Time of Day || City name
== Notation ==
|- valign="top"

| {{time|UTC-05:00|df=y}} || [[New York City|New York]]
=== ISO 8601 ===
|- valign="top" style="border-top:hidden;"
{{Main|ISO 8601}}
| {{time|UTC+04:00|df=y}} || [[Dubai]]

|}
ISO 8601 is a standard established by the [[International Organization for Standardization]] defining methods of representing dates and times in textual form, including specifications for representing time zones.
{| class="wikitable"

! Time of Day || City name
If a time is in [[Coordinated Universal Time]] (UTC), a "Z" is added directly after the time without a separating space. "Z" is the zone designator for the zero UTC offset. "09:30&nbsp;UTC" is therefore represented as "09:30Z" or "0930Z". Likewise, "14:45:15&nbsp;UTC" is written as "14:45:15Z" or "144515Z".<ref name="ZuluTime">{{Cite web|url=https://www.timeanddate.com/time/zones/z|title=Z – Zulu Time Zone (Time Zone Abbreviation)|website=TimeAndDate.com|language=en|access-date=August 22, 2018|archive-date=August 22, 2018|archive-url=https://web.archive.org/web/20180822145905/https://www.timeanddate.com/time/zones/z|url-status=live}}</ref> UTC time is also known as "Zulu" time, since "Zulu" is a [[ICAO spelling alphabet|phonetic alphabet]] code word for the letter "Z".<ref name="ZuluTime"/>
|- valign="top"

| {{time|UTC-05:00|df=y}} || [[New York City|New York]]
[[UTC offset|Offsets from UTC]] are written in the format ±hh:mm, ±hhmm, or ±hh (either hours ahead or behind UTC). For example, if the time being described is one hour ahead of UTC (such as the time in [[Germany]] during the winter), the zone designator would be "[[UTC+01:00|+01:00]]", "+0100", or simply "+01". This numeric representation of time zones is appended to local times in the same way that alphabetic time zone abbreviations (or "Z", as above) are appended. The offset from UTC changes with [[daylight saving time]], e.g. a time offset in [[Chicago]], which is in the [[Central Time Zone (North America)|North American Central Time Zone]], is "[[UTC−06:00|−06:00]]" for the winter (Central Standard Time) and "[[UTC−05:00|−05:00]]" for the summer (Central Daylight Time).<ref>{{Cite web|url=https://www.nhc.noaa.gov/aboututc.shtml|title=What is UTC or GMT Time?|website=National Hurricane Center |access-date=August 22, 2018|archive-date=August 22, 2018|archive-url=https://web.archive.org/web/20180822150019/https://www.nhc.noaa.gov/aboututc.shtml|url-status=live}}</ref>
|- valign="top" style="border-top:hidden;"

| {{time|UTC+09:00|df=y}} || [[Tokyo]]
=== Abbreviations ===
|}
{{Main|List of time zone abbreviations}}
{| class="wikitable"

! Time of Day || City name
Time zones are often represented by alphabetic abbreviations such as "EST", "WST", and "CST", but these are not part of the international time and date standard [[ISO 8601#Time zone designators|ISO 8601]]. Such designations can be ambiguous; for example, "CST" can mean (North American) [[Central Standard Time]] (UTC−06:00), [[Cuba Standard Time]] (UTC−05:00) and [[China Standard Time]] (UTC+08:00), and it is also a widely used variant of ACST ([[Australian Central Standard Time]], UTC+09:30).<ref>"[https://www.timeanddate.com/time/zones/ Time Zone Abbreviations – Worldwide List]", Timeanddate.com. {{Webarchive|url=https://web.archive.org/web/20180821101900/https://www.timeanddate.com/time/zones/ |date=August 21, 2018 }}.</ref>
|- valign="top"

| {{time|UTC-05:00|df=y}} || [[New York City|New York]]
== Conversions ==
|- valign="top" style="border-top:hidden;"
Conversion between time zones obeys the relationship
| {{time|UTC+11:00|df=y}} || [[Sydney]]

|}
: "time in zone A" − "UTC offset for zone A" = "time in zone B" − "UTC offset for zone B",
From [[London]] to other cities:

{| class="wikitable"
in which each side of the equation is equivalent to UTC.
! Time of Day || City name

|- valign="top"
The conversion equation can be rearranged to
| {{time|UTC-05:00|df=y}} || [[New York City|New York]]

|- valign="top" style="border-top:hidden;"
: "time in zone B" = "time in zone A" − "UTC offset for zone A" + "UTC offset for zone B".
| {{time|UTC±00:00|df=y}} || [[London]]

|}
For example, the [[New York Stock Exchange]] opens at 09:30 ([[Eastern time zone|EST]], UTC offset= −05:00). In [[California]] ([[Pacific time zone|PST]], UTC offset= −08:00) and [[India]] ([[Indian standard time|IST]], UTC offset= +05:30), the New York Stock Exchange opens at
{| class="wikitable"

! Time of Day || City name
: time in California = 09:30 − (−05:00) + (−08:00) = 06:30;
|- valign="top"
: time in India = 09:30 − (−05:00) + (+05:30) = 20:00.
| {{time|UTC±00:00|df=y}} || [[London]]

|- valign="top" style="border-top:hidden;"
These calculations become more complicated near the time switch to or from daylight saving time, as the UTC offset for the area becomes a function of UTC time.
| {{time|UTC+01:00|df=y}} || [[Berlin]]
|}
{| class="wikitable"
! Time of Day || City name
|- valign="top"
| {{time|UTC±00:00|df=y}} || [[London]]
|- valign="top" style="border-top:hidden;"
| {{time|UTC+03:00|df=y}} || [[Moscow]]
|}
{| class="wikitable"
! Time of Day || City name
|- valign="top"
| {{time|UTC±00:00|df=y}} || [[London]]
|- valign="top" style="border-top:hidden;"
| {{time|UTC+04:00|df=y}} || [[Dubai]]
|}
{| class="wikitable"
! Time of Day || City name
|- valign="top"
| {{time|UTC±00:00|df=y}} || [[London]]
|- valign="top" style="border-top:hidden;"
| {{time|UTC+09:00|df=y}} || [[Tokyo]]
|}
{| class="wikitable"
! Time of Day || City name
|- valign="top"
| {{time|UTC±00:00|df=y}} || [[London]]
|- valign="top" style="border-top:hidden;"
| {{time|UTC+11:00|df=y}} || [[Sydney]]
|}


The time differences may also result in different dates. For example, when it is 22:00 on Monday in [[Egypt]] (UTC+02:00), it is 01:00 on Tuesday in [[Pakistan]] (UTC+05:00).
==Time zone conversions==

{| class="wikitable collapsible collapsed" style=""
! colspan=52 | Time of day by zone
The table "Time of day by zone" gives an overview on the time relations between different zones.

{| class="wikitable collapsible collapsed nowrap" style="font-size:90%; line-height:1.2; text-align:center"
! colspan=25 style=line-height:1.5 | Time of day by zone
|-
|-
| [[List of UTC time offsets|UTC offset]] || colspan=24 | {{blue|Monday}}
| City, ''Region''
| [[List of time zone abbreviations|Zone]]
| '''°W'''
| colspan=24 align=center | {{color|#ff0000|Tue}}
| colspan=24 align=center | {{color|#00ff00|Wed}}
|
|-
|-
| [[UTC−12:00]] || {{blue|00:00}} || {{blue|01:00}} || {{blue|02:00}} || {{blue|03:00}} || {{blue|04:00}} || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}}
| ''[[American Samoa]]''
| [[Samoa Time Zone|SST]]
| '''165'''
| {{color|#ff0000| 0}}
| {{color|#ff0000| 1}}
| {{color|#ff0000| 2}}
| {{color|#ff0000| 3}}
| {{color|#ff0000| 4}}
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
|-
|-
| [[UTC−11:00]] || {{blue|01:00}} || {{blue|02:00}} || {{blue|03:00}} || {{blue|04:00}} || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}}
| ''[[Hawaii]]''
| [[Hawaii–Aleutian Standard Time|HAST]]
| '''150'''
| {{color|#ff0000| 1}}
| {{color|#ff0000| 2}}
| {{color|#ff0000| 3}}
| {{color|#ff0000| 4}}
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
|-
|-
| [[UTC−10:00]] || {{blue|02:00}} || {{blue|03:00}} || {{blue|04:00}} || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}}
| [[Juneau, Alaska]]
| [[Alaska Time Zone|AKST]]
| '''135'''
| {{color|#ff0000| 2}}
| {{color|#ff0000| 3}}
| {{color|#ff0000| 4}}
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
|-
|-
| [[UTC−09:30]] || {{blue|02:30}} || {{blue|03:30}} || {{blue|04:30}} || {{blue|05:30}} || {{blue|06:30}} || {{blue|07:30}} || {{blue|08:30}} || {{blue|09:30}} || {{blue|10:30}} || {{blue|11:30}} || {{blue|12:30}} || {{blue|13:30}} || {{blue|14:30}} || {{blue|15:30}} || {{blue|16:30}} || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}}
| [[San Francisco]], [[Los Angeles]]
| [[Pacific Time Zone|PST]]
| '''120'''
| {{color|#ff0000| 3}}
| {{color|#ff0000| 4}}
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
|-
|-
| [[UTC−09:00]] || {{blue|03:00}} || {{blue|04:00}} || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}}
| [[Denver]]
| [[Mountain Time Zone|MST]]
| '''105'''
| {{color|#ff0000| 4}}
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
|-
|-
| [[UTC−08:00]] || {{blue|04:00}} || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}}
| [[Winnipeg]], [[Chicago]], [[Mexico City]]
| [[Central Time Zone|CST]]
| '''90'''
| {{color|#ff0000| 5}}
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
|-
|-
| [[UTC−07:00]] || {{blue|05:00}} || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}}
| [[Ottawa]], [[New York City|New York]], [[Miami]], [[Quito]], [[Lima]]
| [[Eastern Time Zone|EST]]
| '''75'''
| {{color|#ff0000| 6}}
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
|-
|-
| [[UTC−06:00]] || {{blue|06:00}} || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}}
| [[Caracas]], [[La Paz]], [[Santiago]]
| [[Chile Standard Time|CLT]]
| '''60'''
| {{color|#ff0000| 7}}
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
|-
|-
| [[UTC−05:00]] || {{blue|07:00}} || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}}
| ''[[Greenland]]'', [[Rio de Janeiro]], [[Buenos Aires]]
| [[Argentina Time|ART]]
| '''45'''
| {{color|#ff0000| 8}}
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
|-
|-
| [[UTC−04:00]] || {{blue|08:00}} || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}}
|
| [[South Georgia and the South Sandwich Islands|GST]]
| '''30'''
| {{color|#ff0000| 9}}
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
|-
|-
| [[UTC−03:30]] || {{blue|08:30}} || {{blue|09:30}} || {{blue|10:30}} || {{blue|11:30}} || {{blue|12:30}} || {{blue|13:30}} || {{blue|14:30}} || {{blue|15:30}} || {{blue|16:30}} || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}}
|
| [[Cape Verde Time|CVT]]
| '''15'''
| {{color|#ff0000|10}}
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
|-
|-
| [[UTC−03:00]] || {{blue|09:00}} || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}}
| [[London]], [[Lisbon]], [[Algiers]], [[Monrovia]]
| [[Coordinated Universal Time|UTC]]
| '''0'''
| {{color|#ff0000|11}}
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
|-
|-
| [[UTC−02:30]] || {{blue|09:30}} || {{blue|10:30}} || {{blue|11:30}} || {{blue|12:30}} || {{blue|13:30}} || {{blue|14:30}} || {{blue|15:30}} || {{blue|16:30}} || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}}
| [[Paris]], [[Rome]], [[Lagos]], [[Kinshasa]]
| [[Central European Time|CET]]
| '''15'''
| {{color|#ff0000|12}}
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
|-
|-
| [[UTC−02:00]] || {{blue|10:00}} || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}}
| [[Helsinki]], [[Moscow]], [[Cairo]], [[Cape Town]]
| [[Eastern European Time|EET]]
| '''30'''
| {{color|#ff0000|13}}
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
|-
|-
| [[UTC−01:00]] || {{blue|11:00}} || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}}
| [[Archangelsk]], [[Ankara]], [[Addis Abeba]]
| [[Arabia Standard Time|AST]]
| '''45'''
| {{color|#ff0000|14}}
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
|-
|-
| [[UTC+00:00]] || {{blue|12:00}} || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}}
| [[Magnitogorsk]], ''[[Mauritius]]'', ''[[Réunion]]''
| [[Gulf Standard Time|GST]]
| '''60'''
| {{color|#ff0000|15}}
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
|-
|-
| [[UTC+01:00]] || {{blue|13:00}} || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}}
| [[Salekhard]], [[Bishkek]], ''[[Kerguelen Islands|Kerguelen]]''
| [[Pakistan Standard Time|PKT]]
| '''75'''
| {{color|#ff0000|16}}
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
|-
|-
| [[UTC+02:00]] || {{blue|14:00}} || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}}
| [[Norilsk]], [[Novosibirsk]]
| [[Bangladesh Standard Time|BST]]
| '''90'''
| {{color|#ff0000|17}}
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
|-
|-
| [[UTC+03:00]] || {{blue|15:00}} || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}}
| [[Irkutsk]], [[Bangkok]], [[Jakarta]]
| [[Indochina Time|ICT]]
| '''105'''
| {{color|#ff0000|18}}
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
|-
|-
| [[UTC+03:30]] || {{blue|15:30}} || {{blue|16:30}} || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}}
| [[Yakutsk]], [[Beijing]], [[Manila]], [[Perth]]
| [[China Standard Time|CST]]
| '''120'''
| {{color|#ff0000|19}}
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
|-
|-
| [[UTC+04:00]] || {{blue|16:00}} || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}}
| [[Vladivostok]], [[Tokyo]]
| [[Japan Standard Time|JST]]
| '''135'''
| {{color|#ff0000|20}}
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
|-
|-
| [[UTC+04:30]] || {{blue|16:30}} || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}} || {{red|15:30}}
| [[Magadan]], [[Sydney]], [[Melbourne]]
| [[Australian Eastern Standard Time|AEST]]
| '''150'''
| {{color|#ff0000|21}}
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
| {{color|#0000ff|21}}
|-
|-
| [[UTC+05:00]] || {{blue|17:00}} || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}}
|
| [[New Caledonia|NCT]]
| '''165'''
| {{color|#ff0000|22}}
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
| {{color|#0000ff|21}}
| {{color|#0000ff|22}}
|-
|-
| [[UTC+05:30]] || {{blue|17:30}} || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}} || {{red|15:30}} || {{red|16:30}}
| ''[[Fiji]]'', [[Wellington]]
| [[Time in New Zealand|NZST]]
| '''180'''
| {{color|#ff0000|23}}
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
| {{color|#0000ff|21}}
| {{color|#0000ff|22}}
| {{color|#0000ff|23}}
|-
|-
| [[UTC+05:45]] || {{blue|17:45}} || {{blue|18:45}} || {{blue|19:45}} || {{blue|20:45}} || {{blue|21:45}} || {{blue|22:45}} || {{blue|23:45}} || {{red|00:45}} || {{red|01:45}} || {{red|02:45}} || {{red|03:45}} || {{red|04:45}} || {{red|05:45}} || {{red|06:45}} || {{red|07:45}} || {{red|08:45}} || {{red|09:45}} || {{red|10:45}} || {{red|11:45}} || {{red|12:45}} || {{red|13:45}} || {{red|14:45}} || {{red|15:45}} || {{red|16:45}}
|''[[Phoenix Islands]]''
|
|
| {{color|#00ff00| 0}}
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
| {{color|#0000ff|21}}
| {{color|#0000ff|22}}
| {{color|#0000ff|23}}
| {{color|#8ddbf9|0}}
|-
|-
| [[UTC+06:00]] || {{blue|18:00}} || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}}
|''[[Line Islands]]''
|
|
| {{color|#00ff00| 1}}
| {{color|#00ff00| 2}}
| {{color|#00ff00| 3}}
| {{color|#00ff00| 4}}
| {{color|#00ff00| 5}}
| {{color|#00ff00| 6}}
| {{color|#00ff00| 7}}
| {{color|#00ff00| 8}}
| {{color|#00ff00| 9}}
| {{color|#00ff00|10}}
| {{color|#00ff00|11}}
| {{color|#00ff00|12}}
| {{color|#00ff00|13}}
| {{color|#00ff00|14}}
| {{color|#00ff00|15}}
| {{color|#00ff00|16}}
| {{color|#00ff00|17}}
| {{color|#00ff00|18}}
| {{color|#00ff00|19}}
| {{color|#00ff00|20}}
| {{color|#00ff00|21}}
| {{color|#00ff00|22}}
| {{color|#00ff00|23}}
| {{color|#0000ff| 0}}
| {{color|#0000ff| 1}}
| {{color|#0000ff| 2}}
| {{color|#0000ff| 3}}
| {{color|#0000ff| 4}}
| {{color|#0000ff| 5}}
| {{color|#0000ff| 6}}
| {{color|#0000ff| 7}}
| {{color|#0000ff| 8}}
| {{color|#0000ff| 9}}
| {{color|#0000ff|10}}
| {{color|#0000ff|11}}
| {{color|#0000ff|12}}
| {{color|#0000ff|13}}
| {{color|#0000ff|14}}
| {{color|#0000ff|15}}
| {{color|#0000ff|16}}
| {{color|#0000ff|17}}
| {{color|#0000ff|18}}
| {{color|#0000ff|19}}
| {{color|#0000ff|20}}
| {{color|#0000ff|21}}
| {{color|#0000ff|22}}
| {{color|#0000ff|23}}
| {{color|#8ddbf9|0}}
| {{color|#8ddbf9|1}}
|-
|-
| [[UTC+06:30]] || {{blue|18:30}} || {{blue|19:30}} || {{blue|20:30}} || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}} || {{red|15:30}} || {{red|16:30}} || {{red|17:30}}
|
|
|-
| [[UTC+07:00]] || {{blue|19:00}} || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}}
| '''°E'''
|-
| colspan=24 align=center | {{color|#00ff00|Wed}}
| [[UTC+08:00]] || {{blue|20:00}} || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}}
| colspan=24 align=center | {{color|#0000ff|Thu}}
|-
| colspan=2 align=center | {{color|#8ddbf9|Fri}}
| [[UTC+08:45]] || {{blue|20:45}} || {{blue|21:45}} || {{blue|22:45}} || {{blue|23:45}} || {{red|00:45}} || {{red|01:45}} || {{red|02:45}} || {{red|03:45}} || {{red|04:45}} || {{red|05:45}} || {{red|06:45}} || {{red|07:45}} || {{red|08:45}} || {{red|09:45}} || {{red|10:45}} || {{red|11:45}} || {{red|12:45}} || {{red|13:45}} || {{red|14:45}} || {{red|15:45}} || {{red|16:45}} || {{red|17:45}} || {{red|18:45}} || {{red|19:45}}
|-
| [[UTC+09:00]] || {{blue|21:00}} || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}}
|-
| [[UTC+09:30]] || {{blue|21:30}} || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}} || {{red|15:30}} || {{red|16:30}} || {{red|17:30}} || {{red|18:30}} || {{red|19:30}} || {{red|20:30}}
|-
| [[UTC+10:00]] || {{blue|22:00}} || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}} || {{red|21:00}}
|-
| [[UTC+10:30]] || {{blue|22:30}} || {{blue|23:30}} || {{red|00:30}} || {{red|01:30}} || {{red|02:30}} || {{red|03:30}} || {{red|04:30}} || {{red|05:30}} || {{red|06:30}} || {{red|07:30}} || {{red|08:30}} || {{red|09:30}} || {{red|10:30}} || {{red|11:30}} || {{red|12:30}} || {{red|13:30}} || {{red|14:30}} || {{red|15:30}} || {{red|16:30}} || {{red|17:30}} || {{red|18:30}} || {{red|19:30}} || {{red|20:30}} || {{red|21:30}}
|-
| [[UTC+11:00]] || {{blue|23:00}} || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}} || {{red|21:00}} || {{red|22:00}}
|-
| [[UTC+12:00]] || {{red|00:00}} || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}} || {{red|21:00}} || {{red|22:00}} || {{red|23:00}}
|-
| [[UTC+12:45]] || {{red|00:45}} || {{red|01:45}} || {{red|02:45}} || {{red|03:45}} || {{red|04:45}} || {{red|05:45}} || {{red|06:45}} || {{red|07:45}} || {{red|08:45}} || {{red|09:45}} || {{red|10:45}} || {{red|11:45}} || {{red|12:45}} || {{red|13:45}} || {{red|14:45}} || {{red|15:45}} || {{red|16:45}} || {{red|17:45}} || {{red|18:45}} || {{red|19:45}} || {{red|20:45}} || {{red|21:45}} || {{red|22:45}} || {{red|23:45}}
|-
| [[UTC+13:00]] || {{red|01:00}} || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}} || {{red|21:00}} || {{red|22:00}} || {{red|23:00}} || {{green|00:00}}
|-
| [[UTC+13:45]] || {{red|01:45}} || {{red|02:45}} || {{red|03:45}} || {{red|04:45}} || {{red|05:45}} || {{red|06:45}} || {{red|07:45}} || {{red|08:45}} || {{red|09:45}} || {{red|10:45}} || {{red|11:45}} || {{red|12:45}} || {{red|13:45}} || {{red|14:45}} || {{red|15:45}} || {{red|16:45}} || {{red|17:45}} || {{red|18:45}} || {{red|19:45}} || {{red|20:45}} || {{red|21:45}} || {{red|22:45}} || {{red|23:45}} || {{green|00:45}}
|-
| [[UTC+14:00]] || {{red|02:00}} || {{red|03:00}} || {{red|04:00}} || {{red|05:00}} || {{red|06:00}} || {{red|07:00}} || {{red|08:00}} || {{red|09:00}} || {{red|10:00}} || {{red|11:00}} || {{red|12:00}} || {{red|13:00}} || {{red|14:00}} || {{red|15:00}} || {{red|16:00}} || {{red|17:00}} || {{red|18:00}} || {{red|19:00}} || {{red|20:00}} || {{red|21:00}} || {{red|22:00}} || {{red|23:00}} || {{green|00:00}} || {{green|01:00}}
|-
| UTC offset || colspan=22 | {{red|Tuesday}} || colspan=2 | {{green|Wednesday}}
|}
|}


Conversion between time zones obeys the relationship
== Nautical time zones ==
{{Main|Nautical time}}
:"time in zone A" − "UTC offset for zone A" = "time in zone B" − "UTC offset for zone B",
in which each side of the equation is equivalent to UTC. (The more familiar term "UTC offset" is used here rather than the term "zone designator" used by the standard.)

The conversion equation can be rearranged to
:"time in zone B" = "time in zone A" − "UTC offset for zone A" + "UTC offset for zone B".

For example, the [[New York Stock Exchange]] opens at 09:30 ([[Eastern time zone|EST]], UTC offset=−05:00). In Los Angeles ([[Pacific time zone|PST]], UTC offset= −08:00) and Delhi ([[Indian standard time|IST]], UTC offset= +05:30), the New York Stock Exchange opens at
:time in Los Angeles = 09:30 − (−05:00) + (−08:00) = 06:30.
:time in Delhi = 09:30 − (−05:00) + (+05:30) = 20:00.

These calculations become more complicated near a daylight saving boundary (because the UTC offset for zone X is a function of the UTC time).

The table "Time of day by zone" gives an overview on the time relations between different zones.


Since the 1920s, a [[nautical time|nautical standard time]] system has been in operation for ships on the [[international waters|high seas]]. As an ideal form of the terrestrial time zone system, nautical time zones consist of [[gore (segment)|gores]] of 15° offset from GMT by a whole number of hours. A nautical date line follows the 180th meridian, bisecting one 15° gore into two 7.5° gores that differ from GMT by ±12 hours.<ref>{{cite book |last=Bowditch |first=Nathaniel |title=American Practical Navigator |location=Washington |publisher=Government Printing Office |orig-date=1925 |date=1975}}</ref><ref>{{cite book |last1=Hill |first1=John C. |author2=Thomas F. Utegaard |author3=Gerard Riordan |title=Dutton's Navigation and Piloting |location=Annapolis |publisher=[[United States Naval Institute]] |date=1958}}</ref><ref>{{cite book |last=Howse |first=Derek |title=Greenwich Time and the Discovery of the Longitude |location=Oxford |publisher=Oxford University Press |date=1980 |isbn=0-19-215948-8}}</ref>
==Nautical time zones==
{{Main article|Nautical time}}
Since the 1920s a [[nautical time|nautical standard time]] system has been in operation for ships on the [[international waters|high seas]]. Nautical time zones are an ideal form of the terrestrial time zone system. Under the system, a time change of one hour is required for each change of longitude by 15°. The 15° [[gore (segment)|gore]] that is offset from GMT or UT1 (not [[Coordinated Universal Time|UTC]]) by twelve hours is bisected by the nautical date line into two 7.5° gores that differ from GMT by ±12 hours. A nautical date line is implied but not explicitly drawn on time zone maps. It follows the 180th meridian except where it is interrupted by [[territorial waters]] adjacent to land, forming gaps: it is a pole-to-pole dashed line.<ref>Bowditch, Nathaniel. ''American Practical Navigator''. Washington: Government Printing Office, 1925, 1939, 1975.</ref><ref>Hill, John C., Thomas F. Utegaard, Gerard Riordan. ''Dutton's Navigation and Piloting''. Annapolis: United States Naval Institute, 1958.</ref><ref>Howse, Derek. ''Greenwich Time and the Discovery of the Longitude''. Oxford: Oxford University Press, 1980. {{ISBN|0-19-215948-8}}.</ref>


However, in practice each ship may choose what time to observe at each location. Ships may decide to adjust their clocks at a convenient time, usually at night, not exactly when they cross a certain longitude.<ref>{{cite web |url=https://www.cruisecritic.com/articles/what-is-cruise-ship-time |title=What Is Cruise Ship Time? Cruise Critic |date=January 7, 2020}}</ref> Some ships simply remain on the time of the departing port during the whole trip.<ref>{{cite web |url=https://caribbeanadventuresroatan.com/frequently-asked-questions/ |title=Frequently Asked Questions |archive-url=https://web.archive.org/web/20210214083749/https://caribbeanadventuresroatan.com/frequently-asked-questions/ |archive-date=February 14, 2021 |url-status=live |website=Caribbean Adventures Roatan}}</ref>
A ship within the territorial waters of any nation would use that nation's standard time, but would revert to nautical standard time upon leaving its territorial waters. The captain is permitted to change the ship's clocks at a time of the captain's choice following the ship's entry into another time zone. The captain often chooses midnight. Ships going in shuttle traffic over a time zone border often keep the same time zone all the time, to avoid confusion about work, meal, and shop opening hours. Still the time table for port calls must follow the land time zone.


==Skewing of zones==<!-- This section is linked from [[daylight saving time]] -->
==Skewing of time zones==
<!-- This section is linked from [[daylight saving time]] -->
[[File:Tzdiff-Europe-summer.png|thumb|Difference between sun time and clock time during daylight saving time:
[[File:Tzdiff-Europe-summer.png|thumb|Difference between sun time and clock time during daylight saving time:
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{{legend|#c00000|DST never observed}}]]
{{legend|#c00000|DST never observed}}]]


Ideal time zones, such as nautical time zones, are based on the mean solar time of a particular meridian located in the middle of that zone with boundaries located 7.5 degrees east and west of the meridian. In practice, zone boundaries are often drawn much farther to the west with often irregular boundaries, and some locations base their time on meridians located far to the east.
Ideal time zones, such as nautical time zones, are based on the mean solar time of a particular meridian in the middle of that zone with boundaries located 7.5 degrees east and west of the meridian. In practice, however, many time zone boundaries are drawn much farther to the west, and some countries are located entirely outside their ideal time zones.


For example, even though the Prime Meridian (0°) passes through [[Spain]] and [[France]], they use the mean solar time of 15 degrees east ([[Central European Time]]) rather than 0 degrees (Greenwich Mean Time). France previously used GMT, but was switched to CET (Central European Time) during the [[German occupation of France during World War II|German occupation]] of the country during World War II and did not switch back after the war.<ref>{{cite journal|last=Poulle|first=Yvonne|title=La France à l'heure allemande|journal=Bibliothèque de l'école des chartes|year=1999|volume=157|issue=2|pages=493–502|url=http://www.persee.fr/articleAsPDF/bec_0373-6237_1999_num_157_2_450989/article_bec_0373-6237_1999_num_157_2_450989.pdf|accessdate=January 11, 2012|doi=10.3406/bec.1999.450989}}</ref> Similarly, prior to World War II, the Netherlands observed "Amsterdam Time", which was twenty minutes ahead of Greenwich Mean Time. They were obliged to follow German time during the war, and kept it thereafter. In the mid 1970s the Netherlands, as with other European states, began observing daylight saving (summer) time.
For example, even though the Prime Meridian (0°) passes through [[Spain]] and [[France]], they use the mean solar time of 15 degrees east ([[Central European Time]]) rather than 0 degrees (Greenwich Mean Time). France previously used GMT, but was switched to CET (Central European Time) during the [[German occupation of France during World War II|German occupation]] of the country during World War II and did not switch back after the war.<ref>{{cite journal|last=Poulle|first=Yvonne|title=La France à l'heure allemande|journal=Bibliothèque de l'École des Chartes|year=1999|volume=157|issue=2|pages=493–502|url=http://www.persee.fr/articleAsPDF/bec_0373-6237_1999_num_157_2_450989/article_bec_0373-6237_1999_num_157_2_450989.pdf|access-date=January 11, 2012|doi=10.3406/bec.1999.450989|archive-date=September 4, 2015|archive-url=https://web.archive.org/web/20150904024453/http://www.persee.fr/articleAsPDF/bec_0373-6237_1999_num_157_2_450989/article_bec_0373-6237_1999_num_157_2_450989.pdf|url-status=live}}</ref> Similarly, prior to World War II, the Netherlands observed "Amsterdam Time", which was twenty minutes ahead of Greenwich Mean Time. They were obliged to follow German time during the war, and kept it thereafter. In the mid-1970s the Netherlands, as other European states, began observing daylight saving (summer) time.


There is a tendency to draw time zone boundaries far to the west of their meridians. The main reason for this is that similar working day schedules around the world have led to people rising on average at 07:00 clock time and going to bed at 23:00 clock time{{citation needed|date=June 2016}}. Another reason is that it can allow the more efficient use of sunlight.<ref>{{cite web|url=http://www.pep.com.cn/200503/ca692073.htm|title=法定时与北京时间|publisher=人民教育出版社|archive-url=https://web.archive.org/web/20061114120456/http://www.pep.com.cn/200503/ca692073.htm|archive-date=November 14, 2006}}</ref> This means that the middle of the period that people are awake ("''awake time noon''") occurs at 15:00 (= [7 + 23]/2) clock time, whereas - if using as clock time the time of the nautical time zone to which the location concerned geographically belongs - solar noon occurs at 12:00 (+/- 30 min) clock time. To make solar noon coincide more with ''awake time noon'' (i.e. make the sun reach its highest point closer to 15:00 clock time rather than 12:00 clock time), the time of one or even two nautical time zones to the east is chosen{{citation needed|reason=The entire section sounds very speculative - many other historical reasons may be possible, please provide evidence for this explanation|date=June 2016}}. Many of these locations also use [[Daylight saving time|DST]], adding yet another nautical time zone to the east. As a result,{{refn|group=note|Spain may have chosen its time zone for other reasons, such as synchronising with trading partners, and adopting CET as a major member of the EU}} in summer, solar noon in the Spanish town of [[Muxía]] occurs at 14:37 clock time, indeed very close to ''awake time noon'' (15:00). This westernmost area of continental Spain never experiences sunset before 18:00 clock time, even in midwinter, despite its lying more than 40 degrees [[Latitude|north]] of the equator. Near the summer [[solstice]], Muxía has sunset times (after 22:00) similar to those of [[Stockholm]], which is in the same time zone and 16 degrees further north. Stockholm has much earlier sunrises, though.
One reason to draw time zone boundaries far to the west of their ideal meridians is to allow the more efficient use of afternoon sunlight.<ref>{{cite web|url=http://www.pep.com.cn/200503/ca692073.htm|title=法定时与北京时间|publisher=人民教育出版社|archive-url=https://web.archive.org/web/20061114120456/http://www.pep.com.cn/200503/ca692073.htm|archive-date=November 14, 2006|language=zh}}</ref> Some of these locations also use [[daylight saving time]] (DST), further increasing the difference to local solar time. As a result, in summer, solar noon in the Spanish city of [[Vigo]] occurs at 14:41 clock time. This westernmost area of continental Spain never experiences sunset before 18:00 clock time, even in winter, despite lying 42 degrees north of the equator.<ref>[https://www.timeanddate.com/sun/spain/vigo Vigo, Galicia, Spain – Sunrise, Sunset, and Daylength] {{Webarchive|url=https://web.archive.org/web/20151110174823/http://www.timeanddate.com/sun/spain/vigo |date=November 10, 2015 }}, Timeanddate.com.</ref> Near the summer [[solstice]], Vigo has sunset times after 22:00, similar to those of [[Stockholm]], which is in the same time zone and 17 degrees farther north. Stockholm has much earlier sunrises, though.<ref>[https://www.timeanddate.com/sun/sweden/stockholm Stockholm, Sweden – Sunrise, Sunset, and Daylength] {{Webarchive|url=https://web.archive.org/web/20210209210704/https://www.timeanddate.com/sun/sweden/stockholm |date=February 9, 2021 }}, Timeanddate.com.</ref>


In the United States, the reasons were more historical and business-related. In Midwestern states, like [[Indiana]] and [[Michigan]], those living in [[Indianapolis]] and [[Detroit]] wanted to be on the same time zone as [[New York City|New York]] to simplify communications and transactions.<ref>{{Cite web |first1=Susannah |last1=Dillion |first2=Hugh |last2=Kremer |title=Indiana does not belong in Eastern Time zone |url=https://www.reporter-times.com/story/opinion/2013/04/02/indiana-does-not-belong-in-eastern-time-zone/47166055/ |access-date=2024-06-06 |website=Reporter-Times |language=en-US}}</ref>
A more extreme example is [[Nome, Alaska]], which is at 165°24′W longitude—just west of center of the idealized [[Samoa Time Zone]] ([[165th meridian west|165°W]]). Nevertheless, Nome observes [[Alaska Time Zone|Alaska Time]] ([[135th meridian west|135°W]]) with DST so it is slightly more than two hours ahead of the sun in winter and over three in summer.<ref>{{cite web|author=Doug O'Hara|title=Alaska: daylight stealing time|work=Far North Science|url=http://www.farnorthscience.com/2007/03/11/news-from-alaska/alaska-daylight-stealing-time/|date=March 11, 2007|accessdate=May 11, 2007}}</ref>
[[Kotzebue, Alaska]], also near the same meridian but north of the Arctic Circle, has an annual event on August 9 to celebrate ''two'' sunsets in the same 24-hour day, one shortly after midnight at the start of the day, and the other shortly before midnight at the end of the day.


A more extreme example is [[Nome, Alaska]], which is at 165°24′W longitude{{snd}}just west of center of the idealized [[Samoa Time Zone]] ([[165th meridian west|165°W]]). Nevertheless, Nome observes [[Alaska Time Zone|Alaska Time]] ([[135th meridian west|135°W]]) with DST so it is slightly more than two hours ahead of the sun in winter and over three in summer.<ref>{{cite web|last=O'Hara|first=Doug|title=Alaska: daylight stealing time|work=Far North Science|url=http://www.farnorthscience.com/2007/03/11/news-from-alaska/alaska-daylight-stealing-time/|date=March 11, 2007|access-date=May 11, 2007|archive-date=September 27, 2007|archive-url=https://web.archive.org/web/20070927094000/http://www.farnorthscience.com/2007/03/11/news-from-alaska/alaska-daylight-stealing-time/|url-status=dead}}</ref>
Also, [[China]] extends as far west as 73°34′E, but all parts of it use [[UTC+08:00]] ([[120th meridian east|120°E]]), so solar "noon" can occur as late as 15:00 in western portions of China such as [[Xinjiang]] and [[Tibet Autonomous Region|Tibet]].
[[Kotzebue, Alaska]], also near the same meridian but north of the Arctic Circle, has ''two'' sunsets on the same day in early August, one shortly after midnight at the start of the day, and the other shortly before midnight at the end of the day.<ref>{{cite web |url=https://www.upi.com/Archives/1986/08/07/Alaskan-village-to-get-two-sunsets-Friday/5874523771200/ |title=Alaskan village to get two sunsets Friday |archive-url=https://web.archive.org/web/20201020163410/https://www.upi.com/Archives/1986/08/07/Alaskan-village-to-get-two-sunsets-Friday/5874523771200/ |archive-date=October 20, 2020 |url-status=live |website=United Press International |date=August 7, 1986}}</ref>

[[List of extreme points of China|China extends as far west as 73°E]], but all parts of it use [[UTC+08:00]] ([[120th meridian east|120°E]]), so solar "noon" can occur as late as 15:00 in western portions of China such as [[Xinjiang]].<ref>[https://www.timeanddate.com/sun/china/kashgar Kashgar, Xinjiang, China – Sunrise, Sunset, and Daylength] {{Webarchive|url=https://web.archive.org/web/20201108141912/https://www.timeanddate.com/sun/china/kashgar |date=November 8, 2020 }}, Timeanddate.com</ref> The [[Afghanistan-China border]] marks the greatest terrestrial time zone difference on Earth, with a 3.5 hour difference between Afghanistan's UTC+4:30 and China's [[Time in China|UTC+08:00]].

{{Wide image|File:Solar time vs standard time.png|800px|align-cap=center|A visualization of the mismatch between clock time and solar time in different locations. In blue areas, clock time lags behind solar time; in red areas, the reverse is true. The two are synchronized in the white areas.}}


== Daylight saving time ==
== Daylight saving time ==
{{Main article|Daylight saving time}}
{{Main|Daylight saving time}}


Many countries, and sometimes just certain regions of countries, adopt daylight saving time (also known as "Summer Time") during part of the year. This typically involves advancing [[clock]]s by an [[hour]] near the start of [[spring (season)|spring]] and adjusting back in [[autumn]] ("spring forward", "fall back"). Modern DST was first proposed in 1907 and was in widespread use in 1916 as a [[World War I|wartime]] measure aimed at [[Energy conservation|conserving coal]]. Despite [[Daylight saving time#Dispute over benefits and drawbacks|controversy]], many countries have used it off and on since then; [[Daylight saving time by country|details vary by location]] and change occasionally. Most countries around the equator do not observe daylight saving time, since the seasonal difference in sunlight is minimal.
Many countries, and sometimes just certain regions of countries, adopt daylight saving time (DST), also known as summer time, during part of the year. This typically involves advancing [[clock]]s by an [[hour]] near the start of [[spring (season)|spring]] and adjusting back in [[autumn]] ("spring forward", "fall back"). Modern DST was first proposed in 1907 and was in widespread use in 1916 as a [[World War I|wartime]] measure aimed at [[Energy conservation|conserving coal]]. Despite [[Daylight saving time#Dispute over benefits and drawbacks|controversy]], many countries have used it off and on since then; [[Daylight saving time by country|details vary by location]] and change occasionally. Countries around the equator usually do not observe daylight saving time, since the seasonal difference in sunlight there is minimal.


==Computer systems and the Internet==
== Computer systems ==
Computer [[operating system]]s include the necessary support for working with all (or almost all) possible local times based on the various time zones. Internally, operating systems typically use [[Coordinated Universal Time|UTC]] as their basic [[system time|time-keeping standard]], while providing services for converting local times to and from UTC, and also the ability to automatically change local time conversions at the start and end of daylight saving time in the various time zones. (See the article on [[Daylight saving time#Computing|daylight saving time]] for more details on this aspect).
Many computer [[operating system]]s include the necessary support for working with all (or almost all) possible local times based on the various time zones. Internally, operating systems typically use [[Coordinated Universal Time|UTC]] as their basic [[system time|time-keeping standard]], while providing services for converting local times to and from UTC, and also the ability to automatically change local time conversions at the start and end of daylight saving time in the various time zones. (See the article on [[Daylight saving time#Computing|daylight saving time]] for more details on this aspect.)


Web servers presenting web pages primarily for an audience in a single time zone or a limited range of time zones typically show times as a local time, perhaps with UTC time in brackets. More internationally oriented websites may show times in UTC only or using an arbitrary time zone. For example, the international English-language version of CNN includes GMT and Hong Kong Time,<ref>{{cite web|url=http://edition.cnn.com |title=International CNN |publisher=Edition.cnn.com |date= |accessdate=December 5, 2011}}</ref> whereas the US version shows [[Eastern Time Zone|Eastern Time]].<ref>{{cite web|url=http://www.cnn.com |title=United States CNN |publisher=Cnn.com |date= |accessdate=December 5, 2011}}</ref> US Eastern Time and [[Pacific Time Zone|Pacific Time]] are also used fairly commonly on many US-based English-language websites with global readership. The format is typically based in the [[World Wide Web Consortium|W3C]] Note "datetime".
Web servers presenting web pages primarily for an audience in a single time zone or a limited range of time zones typically show times as a local time, perhaps with UTC time in brackets. More internationally oriented websites may show times in UTC only or using an arbitrary time zone. For example, the international English-language version of CNN includes GMT and Hong Kong Time,<ref>{{cite web |url=http://edition.cnn.com |title=International CNN |publisher=CNN |access-date=December 5, 2011 |archive-date=March 10, 2018 |archive-url=https://web.archive.org/web/20180310195324/https://edition.cnn.com/ |url-status=live }}</ref> whereas the US version shows [[Eastern Time Zone|Eastern Time]].<ref>{{cite web |url=http://www.cnn.com |title=United States CNN |publisher=Cnn.com |access-date=December 5, 2011 |archive-date=September 11, 2001 |archive-url=https://web.archive.org/web/20010911200318/http://www.cnn.com/ |url-status=live }}</ref> US Eastern Time and [[Pacific Time Zone|Pacific Time]] are also used fairly commonly on many US-based English-language websites with global readership. The format is typically based in the [[World Wide Web Consortium|W3C]] Note "datetime".


[[Email]] systems and other messaging systems ([[Internet Relay Chat|IRC chat]], etc.)<ref>{{cite web|url=https://wiki.ubuntu.com/BuildingCommunity/BookingUbuntuMeetingChannel|title=Guidelines for Ubuntu IRC Meetings|date=August 6, 2008<!-- 15:53:34-->|publisher=[[Canonical Ltd.]]}}</ref> time-stamp messages using UTC, or else include the sender's time zone as part of the message, allowing the receiving program to display the message's date and time of sending in the recipient's local time.
[[Email]] systems and other messaging systems ([[Internet Relay Chat|IRC chat]], etc.)<ref>{{cite web|url=https://wiki.ubuntu.com/BuildingCommunity/BookingUbuntuMeetingChannel|title=Guidelines for Ubuntu IRC Meetings|date=August 6, 2008<!-- 15:53:34-->|publisher=[[Canonical Ltd.]]|access-date=July 13, 2009|archive-date=February 25, 2011|archive-url=https://web.archive.org/web/20110225064621/https://wiki.ubuntu.com/BuildingCommunity/BookingUbuntuMeetingChannel|url-status=live}}</ref> time-stamp messages using UTC, or else include the sender's time zone as part of the message, allowing the receiving program to display the message's date and time of sending in the recipient's local time.


[[Database]] records that include a time stamp typically use UTC, especially when the database is part of a system that spans multiple time zones. The use of local time for time-stamping records is not recommended for time zones that implement daylight saving time because once a year there is a one-hour period when local times are ambiguous.
[[Database]] records that include a time stamp typically use UTC, especially when the database is part of a system that spans multiple time zones. The use of local time for time-stamping records is not recommended for time zones that implement daylight saving time because once a year there is a one-hour period when local times are ambiguous.


[[Calendaring software|Calendar systems]] nowadays usually tie their time stamps to UTC, and show them differently on computers that are in different time zones. That works when having telephone or internet meetings. It works less well when travelling, because the calendar events are assumed to take place in the time zone the computer or smartphone was on when creating the event. The event can be shown at the wrong time. For example, if a New Yorker plans to meet someone in Los Angeles at 9 AM, and makes a calendar entry at 9 AM (which the computer assumes is New York time), the calendar entry will be at 6 AM if taking the computer's time zone. There is also an option in newer versions of [[Microsoft Outlook]] to enter the time zone in which an event will happen, but often not in other calendar systems. Calendaring software must also deal with [[daylight saving time]] (DST). If, for political reasons, the begin and end dates of daylight saving time are changed, calendar entries should stay the same in local time, even though they may shift in UTC time. In Microsoft Outlook, time stamps are therefore stored and communicated without DST offsets.<ref>[https://support.microsoft.com/en-us/kb/2642044 How time zone normalization works in Microsoft Outlook]. Microsoft (2015).</ref> Hence, an appointment in London at noon in the summer will be represented as 12:00 (UTC+00:00) even though the event will actually take place at 13:00 UTC. In [[Google Calendar]], calendar events are stored in UTC (although shown in local time) and might be changed by a time-zone changes,<ref>[https://support.google.com/calendar/answer/37064?hl=en&rd=1 Use Google Calendar in different time zones]. Google Calendar Help (as of Oct. 2015)</ref> although normal daylight saving start and end are compensated for (similar to much other calendar software).
[[Calendaring software|Calendar systems]] nowadays usually tie their time stamps to UTC, and show them differently on computers that are in different time zones. That works when having telephone or internet meetings. It works less well when travelling, because the calendar events are assumed to take place in the time zone the computer or smartphone was on when creating the event. The event can be shown at the wrong time. For example, if a New Yorker plans to meet someone in Los Angeles at 9 am, and makes a calendar entry at 9 am (which the computer assumes is New York time), the calendar entry will be at 6 am if taking the computer's time zone. Calendaring software must also deal with [[daylight saving time]] (DST). If, for political reasons, the begin and end dates of daylight saving time are changed, calendar entries should stay the same in local time, even though they may shift in UTC time.


===Operating systems===
=== Operating systems ===
==== Unix ====
{{refimprove section|date=August 2015}}
{{Main|Unix time}}


[[Unix-like]] systems, including [[Linux]] and [[macOS]], keep system time in [[Unix time]] format, representing the number of seconds that have elapsed since 00:00:00 [[Coordinated Universal Time]] (UTC) on Thursday, January 1, 1970, excluding [[leap second]]s.<ref name="single-unix-spec-4.16">{{cite web|url=http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16|title=The Open Group Base Specifications Issue 7, section 4.16 Seconds Since the Epoch|publisher=[[The Open Group]]|access-date=January 22, 2017|archive-date=December 22, 2017|archive-url=https://web.archive.org/web/20171222113543/http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16|url-status=live}}</ref> Unix time is usually converted to local time when displayed to the user, and times specified by the user in local time are converted to Unix time. The conversion takes into account the time zone and daylight saving time rules; by default the time zone and daylight saving time rules are set up when the system is configured, though individual processes can specify time zones and daylight saving time rules using the ''TZ'' [[environment variable]].<ref name="tzset(3)">{{man|sh|tzset|SUS}}</ref> This allows users in multiple time zones, or in the same time zone but with different daylight saving time rules, to use the same computer, with their respective local times displayed correctly to each user. Information about time zones and daylight saving time rules most commonly comes from the [[IANA time zone database]]. Many systems, including anything using the [[GNU C Library]], a C library based on the [[BSD]] C library, or the [[System V Release 4]] C library, can make use of the IANA time zone database.
====Unix====
{{Main article|Unix time}}
Most [[Unix-like]] systems, including [[Linux]] and [[Mac OS X]], keep system time in time_t format, representing the number of seconds that have elapsed since 00:00:00 [[Coordinated Universal Time]] (UTC) on Thursday, January 1, 1970,<ref name="single-unix-spec-4.16">{{cite web|url=http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16|title=The Open Group Base Specifications Issue 7, section 4.16 Seconds Since the Epoch|publisher=[[The Open Group]]|accessdate=January 22, 2017}}</ref>. By default the external representation is as UTC (Coordinated Universal Time), though individual processes can specify time zones using the LC_TIME [[environment variable]] or less commonly the TZ environment variable. This allows users in multiple timezones to use the same computer, with their respective local times displayed correctly to each user. Time zone information most commonly comes from the [[IANA time zone database]]. In fact, many systems, including anything using the [[GNU C Library]], can make use of this database.


====Microsoft Windows====
==== Microsoft Windows ====
[[Microsoft Windows|Windows]]-based computer systems prior to [[Windows 2000]] used local time, but Windows 2000 and later can use UTC as the basic system time.<ref>{{cite web|url=http://msdn.microsoft.com/en-us/library/windows/desktop/ms724390(v=vs.85).aspx|title=GetSystemTime function (Windows)|website=msdn.microsoft.com|accessdate=February 13, 2018}}</ref> The [[Windows Registry|system registry]] contains time zone information that includes the offset from UTC and rules that indicate the start and end dates for daylight saving in each zone. Interaction with the user normally uses local time, and application software is able to calculate the time in various zones. [[Remote Desktop Services|Terminal Servers]] allow remote computers to redirect their time zone settings to the Terminal Server so that users see the correct time for their time zone in their desktop/application sessions. Terminal Services uses the server base time on the Terminal Server and the client time zone information to calculate the time in the session.
[[Microsoft Windows|Windows]]-based computer systems prior to [[Windows 95]] and [[Windows NT]] used local time, but Windows 95 and later, and Windows NT, base system time on UTC.<ref>{{cite web|url=http://msdn2.microsoft.com/en-us/library/ms724961.aspx|title=System Time|website=[[MSDN]]|archive-url=https://web.archive.org/web/20070227230411/http://msdn2.microsoft.com/en-us/library/ms724961.aspx|archive-date=2007-02-27|url-status=dead}}</ref><ref>{{cite web|url=https://learn.microsoft.com/en-us/windows/win32/sysinfo/system-time|title=System Time|website=[[Microsoft Learn]]|date=January 7, 2021|access-date=April 23, 2024|archive-date=February 24, 2024|archive-url=https://web.archive.org/web/20240224224835/https://learn.microsoft.com/en-us/windows/win32/sysinfo/system-time|url-status=live}}</ref> They allow a program to fetch the system time as UTC, represented as a year, month, day, hour, minute, second, and millisecond;<ref>{{cite web|url=http://msdn2.microsoft.com/en-us/library/ms724390.aspx|title=GetSystemTime|website=MSDN|archive-url=https://web.archive.org/web/20070228030857/http://msdn2.microsoft.com/en-us/library/ms724390.aspx|archive-date=2007-02-28|url-status=dead}}</ref><ref>{{cite web|url=https://learn.microsoft.com/en-us/windows/win32/enwiki/api/sysinfoapi/nf-sysinfoapi-getsystemtime|title=GetSystemTime function (Windows)|website=Microsoft Learn|date=February 22, 2024|access-date=April 23, 2024|archive-date=April 23, 2024|archive-url=https://web.archive.org/web/20240423071349/https://learn.microsoft.com/en-us/windows/win32/enwiki/api/sysinfoapi/nf-sysinfoapi-getsystemtime|url-status=live}}</ref> Windows 95 and later, and Windows NT 3.5 and later, also allow the system time to be fetched as a count of 100 ns units since 1601-01-01 00:00:00 UTC.<ref>{{cite web|url=http://msdn2.microsoft.com/en-us/library/ms724397.aspx|title=GetSystemTimeAsFileTime|website=MSDN|archive-url=https://web.archive.org/web/20070224215258/http://msdn2.microsoft.com/en-us/library/ms724397.aspx|archive-date=2007-02-24|url-status=dead}}</ref><ref>{{cite web|url=https://learn.microsoft.com/en-us/windows/win32/enwiki/api/sysinfoapi/nf-sysinfoapi-getsystemtimeasfiletime|title=GetSystemTimeAsFileTime function (Windows)|website=Microsoft Learn|date=February 22, 2024 |access-date=April 23, 2024}}</ref> The [[Windows Registry|system registry]] contains time zone information that includes the offset from UTC and rules that indicate the start and end dates for daylight saving in each zone. Interaction with the user normally uses local time, and application software is able to calculate the time in various zones. [[Remote Desktop Services|Terminal Servers]] allow remote computers to redirect their time zone settings to the Terminal Server so that users see the correct time for their time zone in their desktop/application sessions. Terminal Services uses the server base time on the Terminal Server and the client time zone information to calculate the time in the session.


===Programming languages===
=== Programming languages ===
==== Java ====
While most application software will use the underlying operating system for time zone and daylight saving time rule information, [[Java (programming language)|the Java Platform]], from version 1.3.1, has maintained its own database of time zone and daylight saving time rule information. This database is updated whenever time zone or daylight saving time rules change. [[Oracle Corporation|Oracle]] provides an updater tool for this purpose.<ref>{{cite web |url=https://www.oracle.com/java/technologies/javase/tzupdater-readme.html |title=Timezone Updater Tool |publisher=Oracle Java Technologies |access-date=November 21, 2024}}</ref>


As an alternative to the information bundled with the Java Platform, programmers may choose to use the Joda-Time library.<ref>{{cite web |url=http://joda-time.sourceforge.net/ |title=Joda-Time |publisher=Joda-time.sourceforge.net |access-date=December 5, 2011 |archive-date=December 3, 2011 |archive-url=https://web.archive.org/web/20111203213457/http://joda-time.sourceforge.net/ |url-status=live }}</ref> This library includes its own data based on the IANA time zone database.<ref>{{cite web |url=http://www.twinsun.com/tz/tz-link.htm |title=tz database |publisher=Twinsun.com |date=December 26, 2007 |access-date=December 5, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20120623013511/http://www.twinsun.com/tz/tz-link.htm |archive-date=June 23, 2012 }}</ref>
====Java====
While most application software will use the underlying operating system for timezone information, [[Java (programming language)|the Java Platform]], from version 1.3.1, has maintained its own timezone database. This database is updated whenever timezone rules change. [[Oracle Corporation|Oracle]] provides an updater tool for this purpose.<ref>{{cite web|url=http://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html |title=Timezone Updater Tool |publisher=Java.sun.com |date= |accessdate=December 5, 2011}}</ref>


As of Java 8 there is a new date and time API that can help with converting times.<ref>{{cite web |url=https://docs.oracle.com/javase/tutorial/datetime/ |title=Java 8 Date Time}}</ref>
As an alternative to the timezone information bundled with the Java Platform, programmers may choose to use the Joda-Time library.<ref>{{cite web|url=http://joda-time.sourceforge.net/ |title=Joda-Time |publisher=Joda-time.sourceforge.net |date= |accessdate=December 5, 2011}}</ref> This library includes its own timezone data based on the IANA time zone database.<ref>{{cite web |url=http://www.twinsun.com/tz/tz-link.htm |title=tz database |publisher=Twinsun.com |date=December 26, 2007 |accessdate=December 5, 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20120623013511/http://www.twinsun.com/tz/tz-link.htm |archivedate=June 23, 2012 |df= }}</ref>


==== JavaScript ====
As of Java 8 new DATE TIME API is there that can help converting timezones.
Traditionally, there was very little in the way of time zone support for [[JavaScript]]. Essentially the programmer had to extract the UTC offset by instantiating a time object, getting a GMT time from it, and differencing the two. This does not provide a solution for more complex daylight saving variations, such as divergent DST directions between northern and southern hemispheres.
[https://docs.oracle.com/javase/tutorial/datetime/ Java 8 Date Time]


ECMA-402, the standard on Internationalization API for JavaScript, provides ways of formatting Time Zones.<ref>{{Cite web
====JavaScript====
| title = ECMAScript 2015 Internationalization API Specification
There is very little in the way of timezone support for [[JavaScript]]. Essentially the programmer has to extract the UTC offset by instantiating a time object, getting a GMT time from it, and differencing the two. This does not provide a solution for daylight saving variations.
| publisher = ECMA International
| date = June 2015
| access-date = September 4, 2019
| url = https://www.ecma-international.org/ecma-402/2.0/#sec-time-zone-names
| archive-date = October 26, 2019
| archive-url = https://web.archive.org/web/20191026140400/https://www.ecma-international.org/ecma-402/2.0/#sec-time-zone-names
| url-status = live
}}</ref> However, due to size constraint, some implementations or distributions do not include it.<ref>{{Cite web
| title = Internationalization Support
| work = Node.js v12.10.0 Documentation
| access-date = September 4, 2019
| url = https://nodejs.org/enwiki/api/intl.html#intl_disable_all_internationalization_features_none
| archive-date = August 28, 2019
| archive-url = https://web.archive.org/web/20190828234745/https://nodejs.org/enwiki/api/intl.html#intl_disable_all_internationalization_features_none
| url-status = live
}}</ref>


====Perl====
==== Perl ====
The DateTime object in [[Perl]] supports all time zones in the [[Tz database|Olson DB]] and includes the ability to get, set and convert between time zones.<ref>{{cite web|url=https://metacpan.org/pod/DateTime |title=DateTime |publisher=METACPAN |date= |accessdate=April 14, 2014}}</ref>
The DateTime object in [[Perl]] supports all entries in the [[IANA time zone database]] and includes the ability to get, set and convert between time zones.<ref>{{cite web |url=https://metacpan.org/pod/DateTime |title=DateTime |publisher=METACPAN |access-date=April 14, 2014 |archive-date=March 29, 2014 |archive-url=https://web.archive.org/web/20140329001557/https://metacpan.org/pod/DateTime |url-status=live }}</ref>


====PHP====
==== PHP ====
The DateTime objects and related functions have been compiled into the [[PHP]] core since 5.2. This includes the ability to get and set the default script timezone, and DateTime is aware of its own timezone internally. PHP.net provides extensive documentation on this.<ref>{{cite web|url=http://www.php.net/manual/en/book.datetime.php |title=DateTime |publisher=Php.net |date= |accessdate=December 5, 2011}}</ref> As noted there, the most current timezone database can be implemented via the [[PEAR#PECL|PECL]] timezonedb.
The DateTime objects and related functions have been compiled into the [[PHP]] core since 5.2. This includes the ability to get and set the default script time zone, and DateTime is aware of its own time zone internally. PHP.net provides extensive documentation on this.<ref>{{cite web |url=http://www.php.net/manual/en/book.datetime.php |title=DateTime |publisher=Php.net |access-date=December 5, 2011 |archive-date=November 22, 2011 |archive-url=https://web.archive.org/web/20111122174518/http://www.php.net/manual/en/book.datetime.php |url-status=live }}</ref> As noted there, the most current time zone database can be implemented via the [[PEAR#PECL|PECL]] timezonedb.


====Python====
==== Python ====
The standard module datetime included with [[Python (programming language)|Python]] stores and operates on the timezone information class tzinfo. The third party pytz module provides access to the full IANA time zone database.<ref>{{cite web|author=|url=http://pytz.sourceforge.net/ |title=pytz module |publisher=Pytz.sourceforge.net |date= |accessdate=December 5, 2011}}</ref> Negated time zone offset in seconds is stored time.timezone and time.altzone attributes.
The standard module datetime included with [[Python (programming language)|Python]] stores and operates on the time zone information class tzinfo. The third party pytz module provides access to the full IANA time zone database.<ref>{{cite web |url=http://pytz.sourceforge.net/ |title=pytz module |publisher=Pytz.sourceforge.net |access-date=December 5, 2011 |archive-date=November 30, 2011 |archive-url=https://web.archive.org/web/20111130085600/http://pytz.sourceforge.net/ |url-status=live }}</ref> Negated time zone offset in seconds is stored time.timezone and time.altzone attributes. From Python 3.9, the zoneinfo module introduces timezone management without need for third party module.<ref>{{cite web |url=https://docs.python.org/3/library/zoneinfo.html |title=zoneinfo module |publisher=www.python.org |access-date=February 8, 2021 |archive-date=February 7, 2021 |archive-url=https://web.archive.org/web/20210207193618/https://docs.python.org/3/library/zoneinfo.html |url-status=live }}</ref>


====Smalltalk====
==== Smalltalk ====
Each [[Smalltalk]] dialect comes with its own built-in classes for dates, times and timestamps, only a few of which implement the DateAndTime and Duration classes as specified by the ANSI Smalltalk Standard. [[VisualWorks]] provides a TimeZone class that supports up to two annually recurring offset transitions, which are assumed to apply to all years (same behavior as Windows time zones). [[Squeak]] provides a Timezone class that does not support any offset transitions. [[Dolphin Smalltalk]] does not support time zones at all.
Each [[Smalltalk]] dialect comes with its own built-in classes for dates, times and timestamps, only a few of which implement the DateAndTime and Duration classes as specified by the ANSI Smalltalk Standard. [[VisualWorks]] provides a TimeZone class that supports up to two annually recurring offset transitions, which are assumed to apply to all years (same behavior as Windows time zones). [[Squeak]] provides a Timezone class that does not support any offset transitions. [[Dolphin Smalltalk]] does not support time zones at all.


For full support of the tz database (zoneinfo) in a Smalltalk application (including support for any number of annually recurring offset transitions, and support for different intra-year offset transition rules in different years) the third-party, open-source, ANSI-Smalltalk-compliant Chronos Date/Time Library is available for use with any of the following Smalltalk dialects: VisualWorks, Squeak, Gemstone, or Dolphin.<ref>[http://www.chronos-st.org/ Chronos Date/Time Library] {{webarchive |url=https://web.archive.org/web/20140405043602/http://www.chronos-st.org/ |date=April 5, 2014 }}</ref>
For full support of the tz database (zoneinfo) in a Smalltalk application (including support for any number of annually recurring offset transitions, and support for different intra-year offset transition rules in different years) the third-party, open-source, ANSI-Smalltalk-compliant Chronos Date/Time Library is available for use with any of the following Smalltalk dialects: VisualWorks, Squeak, Gemstone, or Dolphin.<ref>[http://www.chronos-st.org/ Chronos Date/Time Library] {{webarchive |url=https://web.archive.org/web/20140405043602/http://www.chronos-st.org/ |date=April 5, 2014 }}</ref>


==Time zones in outer space==
== Time in outer space ==
Orbiting spacecraft may experience many sunrises and sunsets, or none, in a 24-hour period. Therefore, it is not possible to calibrate the time with respect to the Sun and still respect a 24-hour sleep/wake cycle. A common practice for [[space exploration]] is to use the Earth-based time of the launch site or mission control, synchronizing the sleeping cycles of the crew and controllers. The [[International Space Station]] normally uses Greenwich Mean Time (GMT).<ref>{{cite web|title=Ask the Crew: STS-111|url=http://www.spaceflight.nasa.gov/feedback/expert/answer/crew/sts-111/index.html|publisher=National Aeronautics and Space Administration|date=June 19, 2002|access-date=September 10, 2015|archive-date=September 28, 2015|archive-url=https://web.archive.org/web/20150928070925/http://spaceflight.nasa.gov/feedback/expert/answer/crew/sts-111/index.html|url-status=dead}}</ref><ref>{{cite web|title=Day in the Life|url=http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter9.html|last=Lu|first=Ed|publisher=National Aeronautics and Space Administration|date=September 8, 2003|access-date=September 10, 2015|archive-date=September 1, 2012|archive-url=https://web.archive.org/web/20120901183936/http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter9.html|url-status=dead}}</ref>
{{refimprove section|date=September 2015}}
Orbiting spacecraft typically experience many sunrises and sunsets in a 24-hour period, or in the case of [[Apollo program]] astronauts travelling to the moon, none. Thus it is not possible to calibrate time zones with respect to the sun, and still respect a 24-hour sleep/wake cycle. A common practice for [[space exploration]] is to use the Earth-based time zone of the launch site or mission control. This keeps the sleeping cycles of the crew and controllers in sync. The [[International Space Station]] normally uses Greenwich Mean Time (GMT).<ref>{{cite web|title=Ask the Crew: STS-111|url=http://www.spaceflight.nasa.gov/feedback/expert/answer/crew/sts-111/index.html}}</ref><ref>{{cite web|title=Day in the Life|url=http://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter9.html|author=Ed Lu}}</ref>


[[Timekeeping on Mars]] can be more complex, since the planet has a solar day of approximately 24 hours and 39 minutes, known as a [[Timekeeping on Mars#Sols|sol]]. Earth controllers for some Mars missions have synchronized their sleep/wake cycles with the Martian day,<ref>Megan Gannon, 2008, [http://www.space.com/17815-mars-rover-jet-lag.html New Tricks Could Help Mars Rover Team Live on Mars Time], ''space.com''</ref> because solar-powered rover activity on the surface was tied to periods of light and dark. The difference in day length caused the sleep/wake cycles to slowly drift with respect to the day/night cycles on Earth, repeating approximately once every 36 days.
[[Timekeeping on Mars]] can be more complex, since the planet has a solar day of approximately 24 hours and 40 minutes, known as a [[Sol (day on Mars)|sol]]. Earth controllers for some Mars missions have synchronized their sleep/wake cycles with the Martian day, when specifically solar-powered rover activity occurs.<ref>{{cite web |url=https://www.space.com/17815-mars-rover-jet-lag.html |title=New Tricks Could Help Mars Rover Team Live on Mars Time |author=Megan Gannon |website=Space.com |date=September 28, 2012}}</ref>


==See also==
== See also ==
{{portal|Geography|World}}
[[File:Coventry Time Zone Clock.jpg|thumb|right|The control panel of the Time Zone Clock in front of [[Coventry Transport Museum]].]]
* [[Daylight saving time]]
* [[Jet lag]]
* [[ISO 8601]]
* [[Lists of time zones]]
* [[Lists of time zones]]
* [[Time in Europe]]
* [[Metric time]]
* [[Metric time]]
* [[:Category:Time by country|Time by country]]
* [[:Category:Time by country|Time by country]]
* [[World clock]]
* [[Time in Europe]]
* {{annotated link|Abolition of time zones}}
* [[Jet lag]]
* {{annotated link|World clock}}
* {{annotated link|International Date Line}}


==Notes==
== Notes ==
{{notelist}}
{{reflist|group=note}}


==References==
== References ==
{{reflist|30em}}
{{reflist}}


==External links==
== Sources ==
* {{cite encyclopedia | last = Asimov | first = Isaac | encyclopedia = Asimov's Biographical Encyclopedia of Science and Technology: The Living Stories of More than 1000 Great Scientists from the Age of Greece to the Space Age | year = 1964 | publisher = Doubleday & Company, Inc. | location = Garden City, NY | pages = 343–344 | title = Abbe, Cleveland | lccn = 64016199 }}
{{Wikivoyage|Time zones}}
* {{cite encyclopedia | editor-last = Debus | editor-first = Allen G. | encyclopedia = World Who's Who in Science: A Biographical Dictionary of Notable Scientists from Antiquity to the Present | edition = 1st | title=Abbe, Cleveland | publisher = A. N. Marquis Company | location = Chicago, IL | date = 1968 | isbn = 0-8379-1001-3 | lccn = 68056149 | url-access = registration | url = https://archive.org/details/worldwhoswhoinsc0000unse }}
* {{Commons category inline|Time zones}}


== Further reading ==
*{{cite news
| last = Biswas
| first = Soutik
| title = How India's single time zone is hurting its people
| publisher = [[BBC News]]
| date = February 12, 2019
| url = https://www.bbc.com/news/world-asia-india-47168359
| access-date = February 12, 2019}}
*{{cite web
| author = Maulik Jagnani, economist at [[Cornell University]]
| title = PoorSleep: Sunset Time and Human Capital Production
| format = Job Market Paper
| date = January 15, 2019
| url = https://www.dropbox.com/s/5ojttz8d9leco4n/jagnani_jmp.pdf?dl=0
| access-date = February 12, 2019}}
*{{cite web
| title = Time Bandits: The countries rebelling against GMT
| publisher = [[BBC News]]
| format = Video
| date = August 14, 2015
| url = https://www.bbc.com/news/av/world-asia-pacific-33938952/time-bandits-the-countries-rebelling-against-gmt
| access-date = February 12, 2019}}
*{{cite news
| title = How time zones confused the world
| work = [[BBC News]]
| date = August 7, 2015
| url = https://www.bbc.com/news/world-asia-33815153
| access-date = February 12, 2019}}
*{{cite news
| last = Lane
| first = Megan
| title = How does a country change its time zone?
| publisher = [[BBC News]]
| date = May 10, 2011
| url = https://www.bbc.com/news/world-13334229
| access-date = February 12, 2019}}
*{{cite web
| title = A brief history of time zones
| publisher = [[BBC News]]
| format = Video
| date = March 24, 2011
| url = https://www.bbc.com/news/av/science-environment-12787502/a-brief-history-of-time-zones
| access-date = February 12, 2019}}
* {{cite IETF |rfc=8536|title=The Time Zone Information Format (TZif)}}

== External links ==
{{Wikivoyage|Time zones}}
* {{Commons category-inline|Time zones}}
{{UTC time offsets}}
{{Time Topics}}
{{Time Topics}}
{{Earth}}
{{Time measurement and standards}}
{{Time measurement and standards}}

{{Authority control}}
{{Authority control}}
{{DEFAULTSORT:Time Zone}}


[[Category:Time zones]]
[[Category:Time zones| ]]

Latest revision as of 20:06, 26 December 2024

This article is about time zones in general. For a list of time zones by country, see List of time zones by country. For more time zone lists, see Lists of time zones. For other uses, see Time zone (disambiguation).

Time zones of the world

A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it is convenient for areas in frequent communication to keep the same time.

Each time zone is defined by a standard offset from Coordinated Universal Time (UTC). The offsets range from UTC−12:00 to UTC+14:00, and are usually a whole number of hours, but a few zones are offset by an additional 30 or 45 minutes, such as in India and Nepal. Some areas in a time zone may use a different offset for part of the year, typically one hour ahead during spring and summer, a practice known as daylight saving time (DST).

List of UTC offsets

Main article: List of UTC time offsets
Time zones of the world

In the table below, the locations that use daylight saving time (DST) are listed in their UTC offset when DST is not in effect. When DST is in effect, approximately during spring and summer, their UTC offset is increased by one hour (except for Lord Howe Island, where it is increased by 30 minutes). For example, during the DST period California observes UTC−07:00 and the United Kingdom observes UTC+01:00.

UTC offset Locations that do not use DST Locations that use DST
UTC−12:00
UTC−11:00
UTC−10:00
 Cook Islands
 French Polynesia (most)
 Johnston Atoll
 United States: Hawaii
  United States: Andreanof Islands, Islands of Four Mountains, Near Islands, Rat Islands (Aleutian Islands, Alaska)
UTC−09:30  French Polynesia: Marquesas Islands
UTC−09:00  French Polynesia: Gambier Islands  United States: Alaska (most)
UTC−08:00  Clipperton Island
 Pitcairn Islands
UTC−07:00  Canada: British Columbia (northeast), Yukon
 Mexico: Baja California Sur, Nayarit (most), Sinaloa, Sonora
 United States: Arizona (most) 		 Canada: Alberta, British Columbia (southeast), Northwest Territories, Nunavut (west), Saskatchewan (Lloydminster area)
 Mexico: Chihuahua (northwest border)
 United States: Arizona (Navajo Nation), Colorado, Idaho (most), Kansas (west), Montana, Nebraska (west), New Mexico, Nevada (northeast border), North Dakota (southwest), Oregon (east), South Dakota (west), Texas (west), Utah, Wyoming
UTC−06:00
 Canada: Manitoba, Nunavut (central), Ontario (west)
 Chile: Easter Island
 Mexico (northeast border)
 United States: Alabama, Arkansas, Florida (northwest), Illinois, Indiana (northwest, southwest), Iowa, Kansas (most), Kentucky (west), Louisiana, Michigan (northwest border), Minnesota, Mississippi, Missouri, Nebraska (most), North Dakota (most), Oklahoma, South Dakota (most), Tennessee (most), Texas (most), Wisconsin
UTC−05:00
UTC−04:00  Bermuda
 Canada: Labrador (most), New Brunswick, Nova Scotia, Prince Edward Island
 Chile (most)
 Greenland: Pituffik Space Base
UTC−03:30  Canada: Newfoundland, Labrador (southeast)
UTC−03:00  Saint Pierre and Miquelon
UTC−02:00  Brazil: Fernando de Noronha
 South Georgia and the South Sandwich Islands 		 Greenland (most)
UTC−01:00  Cape Verde  Portugal: Azores
UTC+00:00  Faroe Islands
 Guernsey
 Ireland
 Isle of Man
 Jersey
 Portugal (most)
 Spain: Canary Islands
 United Kingdom
UTC+01:00
UTC+02:00
UTC+03:00
UTC+03:30  Iran
UTC+04:00
UTC+04:30  Afghanistan
UTC+05:00
UTC+05:30
UTC+05:45  Nepal
UTC+06:00
UTC+06:30
UTC+07:00
UTC+08:00
UTC+08:45  Australia: Eucla
UTC+09:00
UTC+09:30  Australia: Northern Territory  Australia: South Australia, Yancowinna County[5]
UTC+10:00  Australia: Australian Capital Territory, Jervis Bay Territory, New South Wales (most), Tasmania, Victoria
UTC+10:30  Australia: Lord Howe Island (DST increase is 30 minutes)
UTC+11:00  Norfolk Island
UTC+12:00  New Zealand (most)
UTC+12:45  New Zealand: Chatham Islands
UTC+13:00
UTC+14:00  Kiribati: Line Islands

History

World time clock, 2.5 m high. Made in Dresden 1690. Technical Instrument Museum, Dresden

The apparent position of the Sun in the sky, and thus solar time, varies by location due to the spherical shape of the Earth. This variation corresponds to four minutes of time for every degree of longitude, so for example when it is solar noon in London, it is about 10 minutes before solar noon in Bristol, which is about 2.5 degrees to the west.[6]

The Royal Observatory, Greenwich, founded in 1675, established Greenwich Mean Time (GMT), the mean solar time at that location, as an aid to mariners to determine longitude at sea, providing a standard reference time while each location in England kept a different time.

Railway time

Main article: Railway time
Plaque commemorating the Railway General Time Convention of 1883 in North America
The control panel of the Time Zone Clock in front of Coventry Transport Museum

In the 19th century, as transportation and telecommunications improved, it became increasingly inconvenient for each location to observe its own solar time. In November 1840, the British Great Western Railway started using GMT kept by portable chronometers.[7][failed verification] This practice was soon followed by other railway companies in Great Britain and became known as railway time.

Around August 23, 1852, time signals were first transmitted by telegraph from the Royal Observatory. By 1855, 98% of Great Britain's public clocks were using GMT, but it was not made the island's legal time until August 2, 1880. Some British clocks from this period have two minute hands, one for the local time and one for GMT.[8]

On November 2, 1868, the British Colony of New Zealand officially adopted a standard time to be observed throughout the colony.[9] It was based on longitude 172°30′ east of Greenwich, that is 11 hours 30 minutes ahead of GMT. This standard was known as New Zealand Mean Time.[10]

1913 time zone map of the United States, showing boundaries very different from today

Timekeeping on North American railroads in the 19th century was complex. Each railroad used its own standard time, usually based on the local time of its headquarters or most important terminus, and the railroad's train schedules were published using its own time. Some junctions served by several railroads had a clock for each railroad, each showing a different time.[11] Because of this a number of accidents occurred when trains from different companies using the same tracks mistimed their passings.[12]

Around 1863, Charles F. Dowd proposed a system of hourly standard time zones for North American railroads, although he published nothing on the matter at that time and did not consult railroad officials until 1869. In 1870 he proposed four ideal time zones having north–south borders, the first centered on Washington, D.C., but by 1872 the first was centered on meridian 75° west of Greenwich, with natural borders such as sections of the Appalachian Mountains. Dowd's system was never accepted by North American railroads. Chief meteorologist at the United States Weather Bureau Cleveland Abbe divided the United States into four standard time zones for consistency among the weather stations. In 1879, he published a paper titled Report on Standard Time.[13] In 1883, he convinced North American railroad companies to adopt his time-zone system. In 1884, Britain, which had already adopted its own standard time system for England, Scotland, and Wales, helped gather international consent for global time. In time, the American government, influenced in part by Abbe's 1879 paper, adopted the time-zone system.[14] It was a version proposed by William F. Allen, the editor of the Traveler's Official Railway Guide.[15] The borders of its time zones ran through railroad stations, often in major cities. For example, the border between its Eastern and Central time zones ran through Detroit, Buffalo, Pittsburgh, Atlanta, and Charleston. It was inaugurated on Sunday, November 18, 1883, also called "The Day of Two Noons",[16] when each railroad station clock was reset as standard-time noon was reached within each time zone.

The North American zones were named Intercolonial, Eastern, Central, Mountain, and Pacific. Within a year 85% of all cities with populations over 10,000 (about 200 cities) were using standard time.[17] A notable exception was Detroit (located about halfway between the meridians of Eastern and Central time), which kept local time until 1900, then tried Central Standard Time, local mean time, and Eastern Standard Time (EST) before a May 1915 ordinance settled on EST and was ratified by popular vote in August 1916. The confusion of times came to an end when standard time zones were formally adopted by the U.S. Congress in the Standard Time Act of March 19, 1918.

Worldwide time zones

"World time" redirects here. For the global time standard, see Universal Time.

Italian mathematician Quirico Filopanti introduced the idea of a worldwide system of time zones in his book Miranda!, published in 1858. He proposed 24 hourly time zones, which he called "longitudinal days", the first centred on the meridian of Rome. He also proposed a universal time to be used in astronomy and telegraphy. However, his book attracted no attention until long after his death.[18][19]

Scottish-born Canadian Sir Sandford Fleming proposed a worldwide system of time zones in 1876 - see Sandford Fleming § Inventor of worldwide standard time. The proposal divided the world into twenty-four time zones labeled A-Y (skipping J), each one covering 15 degrees of longitude. All clocks within each zone would be set to the same time as the others, but differed by one hour from those in the neighboring zones.[20] He advocated his system at several international conferences, including the International Meridian Conference, where it received some consideration. The system has not been directly adopted, but some maps divide the world into 24 time zones and assign letters to them, similarly to Fleming's system.[21]

World map of time zones in 1928

By about 1900, almost all inhabited places on Earth had adopted a standard time zone, but only some of them used an hourly offset from GMT. Many applied the time at a local astronomical observatory to an entire country, without any reference to GMT. It took many decades before all time zones were based on some standard offset from GMT or Coordinated Universal Time (UTC). By 1929, the majority of countries had adopted hourly time zones, though some countries such as Iran, India, Myanmar and parts of Australia had time zones with a 30-minute offset. Nepal was the last country to adopt a standard offset, shifting slightly to UTC+05:45 in 1986.[22]

All nations currently use standard time zones for secular purposes, but not all of them apply the concept as originally conceived. Several countries and subdivisions use half-hour or quarter-hour deviations from standard time. Some countries, such as China and India, use a single time zone even though the extent of their territory far exceeds the ideal 15° of longitude for one hour; other countries, such as Spain and Argentina, use standard hour-based offsets, but not necessarily those that would be determined by their geographical location. The consequences, in some areas, can affect the lives of local citizens, and in extreme cases contribute to larger political issues, such as in the western reaches of China.[23] In Russia, which has 11 time zones, two time zones were removed in 2010[24][25] and reinstated in 2014.[26]

Notation

ISO 8601

Main article: ISO 8601

ISO 8601 is a standard established by the International Organization for Standardization defining methods of representing dates and times in textual form, including specifications for representing time zones.

If a time is in Coordinated Universal Time (UTC), a "Z" is added directly after the time without a separating space. "Z" is the zone designator for the zero UTC offset. "09:30 UTC" is therefore represented as "09:30Z" or "0930Z". Likewise, "14:45:15 UTC" is written as "14:45:15Z" or "144515Z".[27] UTC time is also known as "Zulu" time, since "Zulu" is a phonetic alphabet code word for the letter "Z".[27]

Offsets from UTC are written in the format ±hh:mm, ±hhmm, or ±hh (either hours ahead or behind UTC). For example, if the time being described is one hour ahead of UTC (such as the time in Germany during the winter), the zone designator would be "+01:00", "+0100", or simply "+01". This numeric representation of time zones is appended to local times in the same way that alphabetic time zone abbreviations (or "Z", as above) are appended. The offset from UTC changes with daylight saving time, e.g. a time offset in Chicago, which is in the North American Central Time Zone, is "−06:00" for the winter (Central Standard Time) and "−05:00" for the summer (Central Daylight Time).[28]

Abbreviations

Main article: List of time zone abbreviations

Time zones are often represented by alphabetic abbreviations such as "EST", "WST", and "CST", but these are not part of the international time and date standard ISO 8601. Such designations can be ambiguous; for example, "CST" can mean (North American) Central Standard Time (UTC−06:00), Cuba Standard Time (UTC−05:00) and China Standard Time (UTC+08:00), and it is also a widely used variant of ACST (Australian Central Standard Time, UTC+09:30).[29]

Conversions

Conversion between time zones obeys the relationship

"time in zone A" − "UTC offset for zone A" = "time in zone B" − "UTC offset for zone B",

in which each side of the equation is equivalent to UTC.

The conversion equation can be rearranged to

"time in zone B" = "time in zone A" − "UTC offset for zone A" + "UTC offset for zone B".

For example, the New York Stock Exchange opens at 09:30 (EST, UTC offset= −05:00). In California (PST, UTC offset= −08:00) and India (IST, UTC offset= +05:30), the New York Stock Exchange opens at

time in California = 09:30 − (−05:00) + (−08:00) = 06:30;
time in India = 09:30 − (−05:00) + (+05:30) = 20:00.

These calculations become more complicated near the time switch to or from daylight saving time, as the UTC offset for the area becomes a function of UTC time.

The time differences may also result in different dates. For example, when it is 22:00 on Monday in Egypt (UTC+02:00), it is 01:00 on Tuesday in Pakistan (UTC+05:00).

The table "Time of day by zone" gives an overview on the time relations between different zones.

Nautical time zones

Main article: Nautical time

Since the 1920s, a nautical standard time system has been in operation for ships on the high seas. As an ideal form of the terrestrial time zone system, nautical time zones consist of gores of 15° offset from GMT by a whole number of hours. A nautical date line follows the 180th meridian, bisecting one 15° gore into two 7.5° gores that differ from GMT by ±12 hours.[30][31][32]

However, in practice each ship may choose what time to observe at each location. Ships may decide to adjust their clocks at a convenient time, usually at night, not exactly when they cross a certain longitude.[33] Some ships simply remain on the time of the departing port during the whole trip.[34]

Skewing of time zones

Difference between sun time and clock time during daylight saving time:
1h ± 30 min behind
0h ± 30m
1h ± 30 m ahead
2h ± 30 m ahead
3h ± 30 m ahead
  DST observed
  DST formerly observed
  DST never observed

Ideal time zones, such as nautical time zones, are based on the mean solar time of a particular meridian in the middle of that zone with boundaries located 7.5 degrees east and west of the meridian. In practice, however, many time zone boundaries are drawn much farther to the west, and some countries are located entirely outside their ideal time zones.

For example, even though the Prime Meridian (0°) passes through Spain and France, they use the mean solar time of 15 degrees east (Central European Time) rather than 0 degrees (Greenwich Mean Time). France previously used GMT, but was switched to CET (Central European Time) during the German occupation of the country during World War II and did not switch back after the war.[35] Similarly, prior to World War II, the Netherlands observed "Amsterdam Time", which was twenty minutes ahead of Greenwich Mean Time. They were obliged to follow German time during the war, and kept it thereafter. In the mid-1970s the Netherlands, as other European states, began observing daylight saving (summer) time.

One reason to draw time zone boundaries far to the west of their ideal meridians is to allow the more efficient use of afternoon sunlight.[36] Some of these locations also use daylight saving time (DST), further increasing the difference to local solar time. As a result, in summer, solar noon in the Spanish city of Vigo occurs at 14:41 clock time. This westernmost area of continental Spain never experiences sunset before 18:00 clock time, even in winter, despite lying 42 degrees north of the equator.[37] Near the summer solstice, Vigo has sunset times after 22:00, similar to those of Stockholm, which is in the same time zone and 17 degrees farther north. Stockholm has much earlier sunrises, though.[38]

In the United States, the reasons were more historical and business-related. In Midwestern states, like Indiana and Michigan, those living in Indianapolis and Detroit wanted to be on the same time zone as New York to simplify communications and transactions.[39]

A more extreme example is Nome, Alaska, which is at 165°24′W longitude – just west of center of the idealized Samoa Time Zone (165°W). Nevertheless, Nome observes Alaska Time (135°W) with DST so it is slightly more than two hours ahead of the sun in winter and over three in summer.[40] Kotzebue, Alaska, also near the same meridian but north of the Arctic Circle, has two sunsets on the same day in early August, one shortly after midnight at the start of the day, and the other shortly before midnight at the end of the day.[41]

China extends as far west as 73°E, but all parts of it use UTC+08:00 (120°E), so solar "noon" can occur as late as 15:00 in western portions of China such as Xinjiang.[42] The Afghanistan-China border marks the greatest terrestrial time zone difference on Earth, with a 3.5 hour difference between Afghanistan's UTC+4:30 and China's UTC+08:00.

A visualization of the mismatch between clock time and solar time in different locations. In blue areas, clock time lags behind solar time; in red areas, the reverse is true. The two are synchronized in the white areas.

Daylight saving time

Main article: Daylight saving time

Many countries, and sometimes just certain regions of countries, adopt daylight saving time (DST), also known as summer time, during part of the year. This typically involves advancing clocks by an hour near the start of spring and adjusting back in autumn ("spring forward", "fall back"). Modern DST was first proposed in 1907 and was in widespread use in 1916 as a wartime measure aimed at conserving coal. Despite controversy, many countries have used it off and on since then; details vary by location and change occasionally. Countries around the equator usually do not observe daylight saving time, since the seasonal difference in sunlight there is minimal.

Computer systems

Many computer operating systems include the necessary support for working with all (or almost all) possible local times based on the various time zones. Internally, operating systems typically use UTC as their basic time-keeping standard, while providing services for converting local times to and from UTC, and also the ability to automatically change local time conversions at the start and end of daylight saving time in the various time zones. (See the article on daylight saving time for more details on this aspect.)

Web servers presenting web pages primarily for an audience in a single time zone or a limited range of time zones typically show times as a local time, perhaps with UTC time in brackets. More internationally oriented websites may show times in UTC only or using an arbitrary time zone. For example, the international English-language version of CNN includes GMT and Hong Kong Time,[43] whereas the US version shows Eastern Time.[44] US Eastern Time and Pacific Time are also used fairly commonly on many US-based English-language websites with global readership. The format is typically based in the W3C Note "datetime".

Email systems and other messaging systems (IRC chat, etc.)[45] time-stamp messages using UTC, or else include the sender's time zone as part of the message, allowing the receiving program to display the message's date and time of sending in the recipient's local time.

Database records that include a time stamp typically use UTC, especially when the database is part of a system that spans multiple time zones. The use of local time for time-stamping records is not recommended for time zones that implement daylight saving time because once a year there is a one-hour period when local times are ambiguous.

Calendar systems nowadays usually tie their time stamps to UTC, and show them differently on computers that are in different time zones. That works when having telephone or internet meetings. It works less well when travelling, because the calendar events are assumed to take place in the time zone the computer or smartphone was on when creating the event. The event can be shown at the wrong time. For example, if a New Yorker plans to meet someone in Los Angeles at 9 am, and makes a calendar entry at 9 am (which the computer assumes is New York time), the calendar entry will be at 6 am if taking the computer's time zone. Calendaring software must also deal with daylight saving time (DST). If, for political reasons, the begin and end dates of daylight saving time are changed, calendar entries should stay the same in local time, even though they may shift in UTC time.

Operating systems

Unix

Main article: Unix time

Unix-like systems, including Linux and macOS, keep system time in Unix time format, representing the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on Thursday, January 1, 1970, excluding leap seconds.[46] Unix time is usually converted to local time when displayed to the user, and times specified by the user in local time are converted to Unix time. The conversion takes into account the time zone and daylight saving time rules; by default the time zone and daylight saving time rules are set up when the system is configured, though individual processes can specify time zones and daylight saving time rules using the TZ environment variable.[47] This allows users in multiple time zones, or in the same time zone but with different daylight saving time rules, to use the same computer, with their respective local times displayed correctly to each user. Information about time zones and daylight saving time rules most commonly comes from the IANA time zone database. Many systems, including anything using the GNU C Library, a C library based on the BSD C library, or the System V Release 4 C library, can make use of the IANA time zone database.

Microsoft Windows

Windows-based computer systems prior to Windows 95 and Windows NT used local time, but Windows 95 and later, and Windows NT, base system time on UTC.[48][49] They allow a program to fetch the system time as UTC, represented as a year, month, day, hour, minute, second, and millisecond;[50][51] Windows 95 and later, and Windows NT 3.5 and later, also allow the system time to be fetched as a count of 100 ns units since 1601-01-01 00:00:00 UTC.[52][53] The system registry contains time zone information that includes the offset from UTC and rules that indicate the start and end dates for daylight saving in each zone. Interaction with the user normally uses local time, and application software is able to calculate the time in various zones. Terminal Servers allow remote computers to redirect their time zone settings to the Terminal Server so that users see the correct time for their time zone in their desktop/application sessions. Terminal Services uses the server base time on the Terminal Server and the client time zone information to calculate the time in the session.

Programming languages

Java

While most application software will use the underlying operating system for time zone and daylight saving time rule information, the Java Platform, from version 1.3.1, has maintained its own database of time zone and daylight saving time rule information. This database is updated whenever time zone or daylight saving time rules change. Oracle provides an updater tool for this purpose.[54]

As an alternative to the information bundled with the Java Platform, programmers may choose to use the Joda-Time library.[55] This library includes its own data based on the IANA time zone database.[56]

As of Java 8 there is a new date and time API that can help with converting times.[57]

JavaScript

Traditionally, there was very little in the way of time zone support for JavaScript. Essentially the programmer had to extract the UTC offset by instantiating a time object, getting a GMT time from it, and differencing the two. This does not provide a solution for more complex daylight saving variations, such as divergent DST directions between northern and southern hemispheres.

ECMA-402, the standard on Internationalization API for JavaScript, provides ways of formatting Time Zones.[58] However, due to size constraint, some implementations or distributions do not include it.[59]

Perl

The DateTime object in Perl supports all entries in the IANA time zone database and includes the ability to get, set and convert between time zones.[60]

PHP

The DateTime objects and related functions have been compiled into the PHP core since 5.2. This includes the ability to get and set the default script time zone, and DateTime is aware of its own time zone internally. PHP.net provides extensive documentation on this.[61] As noted there, the most current time zone database can be implemented via the PECL timezonedb.

Python

The standard module datetime included with Python stores and operates on the time zone information class tzinfo. The third party pytz module provides access to the full IANA time zone database.[62] Negated time zone offset in seconds is stored time.timezone and time.altzone attributes. From Python 3.9, the zoneinfo module introduces timezone management without need for third party module.[63]

Smalltalk

Each Smalltalk dialect comes with its own built-in classes for dates, times and timestamps, only a few of which implement the DateAndTime and Duration classes as specified by the ANSI Smalltalk Standard. VisualWorks provides a TimeZone class that supports up to two annually recurring offset transitions, which are assumed to apply to all years (same behavior as Windows time zones). Squeak provides a Timezone class that does not support any offset transitions. Dolphin Smalltalk does not support time zones at all.

For full support of the tz database (zoneinfo) in a Smalltalk application (including support for any number of annually recurring offset transitions, and support for different intra-year offset transition rules in different years) the third-party, open-source, ANSI-Smalltalk-compliant Chronos Date/Time Library is available for use with any of the following Smalltalk dialects: VisualWorks, Squeak, Gemstone, or Dolphin.[64]

Time in outer space

Orbiting spacecraft may experience many sunrises and sunsets, or none, in a 24-hour period. Therefore, it is not possible to calibrate the time with respect to the Sun and still respect a 24-hour sleep/wake cycle. A common practice for space exploration is to use the Earth-based time of the launch site or mission control, synchronizing the sleeping cycles of the crew and controllers. The International Space Station normally uses Greenwich Mean Time (GMT).[65][66]

Timekeeping on Mars can be more complex, since the planet has a solar day of approximately 24 hours and 40 minutes, known as a sol. Earth controllers for some Mars missions have synchronized their sleep/wake cycles with the Martian day, when specifically solar-powered rover activity occurs.[67]

See also

Notes

  1. ^ a b Observes UTC+00:00 around Ramadan.[1][2][3]

References

  1. ^ "Morocco Re-Introduces Clock Changes for Ramadan 2019". Timeanddate.com. April 19, 2019. Archived from the original on December 28, 2020.
  2. ^ "Time Zone in Casablanca, Morocco". Timeanddate.com. Archived from the original on March 30, 2021.
  3. ^ "Time Zone in El Aaiún, Western Sahara". Timeanddate.com. Archived from the original on February 14, 2021.
  4. ^ a b "Décret nº 2017-292 du 6 mars 2017 relatif au temps légal français" [Decree no. 2017-292 of 6 March 2017 relative to French legal time] (in French). Légifrance. March 8, 2017. Archived from the original on December 2, 2020.
  5. ^ "Standard Time Act 1987 No 149". New South Wales Government. Retrieved February 29, 2024.
  6. ^ "Latitude and Longitude of World Cities". Infoplease. Archived from the original on May 24, 2011. Retrieved April 18, 2012.
  7. ^ "WESTMINSTER MEDICAL SOCIETY. Saturday, November 21, 1840". The Lancet. 35 (901): 383. December 1840. doi:10.1016/s0140-6736(00)59842-0. ISSN 0140-6736. Archived from the original on March 30, 2021. Retrieved January 27, 2021.
  8. ^ "Bristol Time". GreenwichMeanTime.com. Archived from the original on June 28, 2006. Retrieved December 5, 2011.
  9. ^ "Telegraph line laid across Cook Strait". New Zealand Ministry for Culture and Heritage. Archived from the original on February 18, 2020. Retrieved January 5, 2020.
  10. ^ "Our Time. How we got it. New Zealand's Method. A Lead to the World". Papers Past. Evening Post. p. 10. Archived from the original on October 8, 2013. Retrieved October 2, 2013.
  11. ^ Alfred, Randy (November 18, 2010). "Nov. 18, 1883: Railroad Time Goes Coast to Coast". Wired. Archived from the original on August 19, 2018. Retrieved July 30, 2018.
  12. ^ "America's first time zone". November 10, 2011.
  13. ^ Debus 1968, p. 2
  14. ^ Asimov 1964, p. 344
  15. ^ "Economics of Time Zones" (PDF). Archived from the original (PDF) on May 14, 2012.  (1.89 MB)
  16. ^ "The Times Reports on "the Day of Two Noons"". History Matters. Archived from the original on April 4, 2012. Retrieved December 5, 2011.
  17. ^ "Resolution concerning new standard time by Chicago". Sos.state.il.us. Archived from the original on October 5, 2011. Retrieved December 5, 2011.
  18. ^ "Quirico Filopanti from scienzagiovane, Bologna University, Italy". Archived from the original on January 17, 2013.
  19. ^ "Suggestions from... ...Gianluigi Parmeggiani, Osservatorio Astronomico di Bologna - The origin of time zones". Archived from the original on August 24, 2007.
  20. ^ Fleming, Sandford (1886). "Time-reckoning for the twentieth century". Annual Report of the Board of Regents of the Smithsonian Institution (1): 345–366. Archived from the original on October 5, 2022. Retrieved March 24, 2022. Reprinted in 1889: Time-reckoning for the twentieth century at the Internet Archive.
  21. ^ Stromberg, Joseph (November 18, 2011). "Sandford Fleming Sets the World's Clock". Smithsonian Magazine. Archived from the original on March 24, 2022. Retrieved March 24, 2022.
  22. ^ "Time Zone & Clock Changes in Kathmandu, Nepal". timeanddate.com. Archived from the original on January 22, 2021. Retrieved December 1, 2020.
  23. ^ Schiavenza, Matt (November 5, 2013). "China Only Has One Time Zone—and That's a Problem". The Atlantic. Archived from the original on August 22, 2018. Retrieved August 22, 2018.
  24. ^ "Russia Reduces Number of Time Zones". TimeAndDate.com. March 23, 2010. Archived from the original on August 9, 2020. Retrieved May 31, 2020.
  25. ^ "About Time: Huge country, nine time zones" (Video). BBC. March 22, 2011. Archived from the original on February 13, 2019. Retrieved February 12, 2019.
  26. ^ "Russian clocks to retreat again in winter, 11 time zones return". Reuters. July 2014. Archived from the original on October 28, 2020. Retrieved October 25, 2020.
  27. ^ a b "Z – Zulu Time Zone (Time Zone Abbreviation)". TimeAndDate.com. Archived from the original on August 22, 2018. Retrieved August 22, 2018.
  28. ^ "What is UTC or GMT Time?". National Hurricane Center. Archived from the original on August 22, 2018. Retrieved August 22, 2018.
  29. ^ "Time Zone Abbreviations – Worldwide List", Timeanddate.com. Archived August 21, 2018, at the Wayback Machine.
  30. ^ Bowditch, Nathaniel (1975) [1925]. American Practical Navigator. Washington: Government Printing Office.
  31. ^ Hill, John C.; Thomas F. Utegaard; Gerard Riordan (1958). Dutton's Navigation and Piloting. Annapolis: United States Naval Institute.
  32. ^ Howse, Derek (1980). Greenwich Time and the Discovery of the Longitude. Oxford: Oxford University Press. ISBN 0-19-215948-8.
  33. ^ "What Is Cruise Ship Time? Cruise Critic". January 7, 2020.
  34. ^ "Frequently Asked Questions". Caribbean Adventures Roatan. Archived from the original on February 14, 2021.
  35. ^ Poulle, Yvonne (1999). "La France à l'heure allemande" (PDF). Bibliothèque de l'École des Chartes. 157 (2): 493–502. doi:10.3406/bec.1999.450989. Archived (PDF) from the original on September 4, 2015. Retrieved January 11, 2012.
  36. ^ "法定时与北京时间" (in Chinese). 人民教育出版社. Archived from the original on November 14, 2006.
  37. ^ Vigo, Galicia, Spain – Sunrise, Sunset, and Daylength Archived November 10, 2015, at the Wayback Machine, Timeanddate.com.
  38. ^ Stockholm, Sweden – Sunrise, Sunset, and Daylength Archived February 9, 2021, at the Wayback Machine, Timeanddate.com.
  39. ^ Dillion, Susannah; Kremer, Hugh. "Indiana does not belong in Eastern Time zone". Reporter-Times. Retrieved June 6, 2024.
  40. ^ O'Hara, Doug (March 11, 2007). "Alaska: daylight stealing time". Far North Science. Archived from the original on September 27, 2007. Retrieved May 11, 2007.
  41. ^ "Alaskan village to get two sunsets Friday". United Press International. August 7, 1986. Archived from the original on October 20, 2020.
  42. ^ Kashgar, Xinjiang, China – Sunrise, Sunset, and Daylength Archived November 8, 2020, at the Wayback Machine, Timeanddate.com
  43. ^ "International CNN". CNN. Archived from the original on March 10, 2018. Retrieved December 5, 2011.
  44. ^ "United States CNN". Cnn.com. Archived from the original on September 11, 2001. Retrieved December 5, 2011.
  45. ^ "Guidelines for Ubuntu IRC Meetings". Canonical Ltd. August 6, 2008. Archived from the original on February 25, 2011. Retrieved July 13, 2009.
  46. ^ "The Open Group Base Specifications Issue 7, section 4.16 Seconds Since the Epoch". The Open Group. Archived from the original on December 22, 2017. Retrieved January 22, 2017.
  47. ^ tzset – System Interfaces Reference, The Single UNIX Specification, Version 4 from The Open Group
  48. ^ "System Time". MSDN. Archived from the original on February 27, 2007.
  49. ^ "System Time". Microsoft Learn. January 7, 2021. Archived from the original on February 24, 2024. Retrieved April 23, 2024.
  50. ^ "GetSystemTime". MSDN. Archived from the original on February 28, 2007.
  51. ^ "GetSystemTime function (Windows)". Microsoft Learn. February 22, 2024. Archived from the original on April 23, 2024. Retrieved April 23, 2024.
  52. ^ "GetSystemTimeAsFileTime". MSDN. Archived from the original on February 24, 2007.
  53. ^ "GetSystemTimeAsFileTime function (Windows)". Microsoft Learn. February 22, 2024. Retrieved April 23, 2024.
  54. ^ "Timezone Updater Tool". Oracle Java Technologies. Retrieved November 21, 2024.
  55. ^ "Joda-Time". Joda-time.sourceforge.net. Archived from the original on December 3, 2011. Retrieved December 5, 2011.
  56. ^ "tz database". Twinsun.com. December 26, 2007. Archived from the original on June 23, 2012. Retrieved December 5, 2011.
  57. ^ "Java 8 Date Time".
  58. ^ "ECMAScript 2015 Internationalization API Specification". ECMA International. June 2015. Archived from the original on October 26, 2019. Retrieved September 4, 2019.
  59. ^ "Internationalization Support". Node.js v12.10.0 Documentation. Archived from the original on August 28, 2019. Retrieved September 4, 2019.
  60. ^ "DateTime". METACPAN. Archived from the original on March 29, 2014. Retrieved April 14, 2014.
  61. ^ "DateTime". Php.net. Archived from the original on November 22, 2011. Retrieved December 5, 2011.
  62. ^ "pytz module". Pytz.sourceforge.net. Archived from the original on November 30, 2011. Retrieved December 5, 2011.
  63. ^ "zoneinfo module". www.python.org. Archived from the original on February 7, 2021. Retrieved February 8, 2021.
  64. ^ Chronos Date/Time Library Archived April 5, 2014, at the Wayback Machine
  65. ^ "Ask the Crew: STS-111". National Aeronautics and Space Administration. June 19, 2002. Archived from the original on September 28, 2015. Retrieved September 10, 2015.
  66. ^ Lu, Ed (September 8, 2003). "Day in the Life". National Aeronautics and Space Administration. Archived from the original on September 1, 2012. Retrieved September 10, 2015.
  67. ^ Megan Gannon (September 28, 2012). "New Tricks Could Help Mars Rover Team Live on Mars Time". Space.com.

Sources

  • Asimov, Isaac (1964). "Abbe, Cleveland". Asimov's Biographical Encyclopedia of Science and Technology: The Living Stories of More than 1000 Great Scientists from the Age of Greece to the Space Age. Garden City, NY: Doubleday & Company, Inc. pp. 343–344. LCCN 64016199.
  • Debus, Allen G., ed. (1968). "Abbe, Cleveland". World Who's Who in Science: A Biographical Dictionary of Notable Scientists from Antiquity to the Present (1st ed.). Chicago, IL: A. N. Marquis Company. ISBN 0-8379-1001-3. LCCN 68056149.

Further reading

Wikivoyage has a travel guide for Time zones.
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