Century leap year: Difference between revisions
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{{Short description|Year evenly divisible by 400}} |
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A '''century leap year''' in the [[Gregorian calendar]] is a year that is exactly divisible by 400 (and, thus, as with every other [[leap year]], qualifies for the [[intercalation]] of February 29). The years 1600 and 2000, for example, were century leap years; the century years of 1700, 1800, and 1900 were not century leap years. The next century leap year will occur in [[24th century|2400]]. Century leap years always start on a [[Saturday]], and the February 29 intercalation of such years is always a Tuesday. |
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{{more citations|date=December 2020}} |
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A '''century leap year''' is a [[leap year]] in the [[Gregorian calendar]] that is evenly [[divisible]] by 400.<ref>{{cite web| url=https://aa.usno.navy.mil/faq/calendars | title= Introduction to Calendars | date=n.d.|publisher= [[United States Naval Observatory]] |accessdate=9 May 2022 |quote=Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is.}}</ref> |
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Like all leap years, it has an extra day in February for a total of 366 days instead of 365. In the obsolete [[Julian calendar]], all years that were divisible by 4, including end-of-century years, were considered leap years. The Julian rule, however, adds too many leap days (about 3 extra leap days in 400 years), which resulted in the calendar drifting gradually with respect to the astronomical seasons. To remedy this, [[Pope Gregory XIII]] introduced in 1582 a slightly modified version of the Julian calendar, the [[Gregorian calendar]], where century years are leap years only if they are divisible by 400. This eliminates 3 of the 4 end-of-century years in a 400-year period. For example, the years 1600, 2000, 2400, and 2800 are century leap years since those numbers are evenly divisible by 400, while 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 are [[common year]]s despite being evenly divisible by 4. This scheme brings the average length of the calendar year significantly closer to the astronomical length of the year, nearly eliminating the drift of the calendar against the seasons. |
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The century year "divisible by 400" rule of the Gregorian calendar was considered an improvement over the previously utilized [[Julian calendar]] which had provided for a leap year every four years; this practice resulted, over the centuries, in too many leap days being added to the calendar and placing it out of step with the astronomical seasons. |
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The Gregorian calendar was adopted by various countries at different times over several centuries. Dates prior to 1582 are generally recorded using the Julian calendar, and different countries have different conventions about how to record dates between 1582 and their [[adoption of the Gregorian calendar]].{{efn|See, for example, [[Old Style and New Style dates]].}} Consequently, for example, the year 1700 was a leap year in the British and Russian empires but not in most of the rest of Europe; 1800 and 1900 were still leap years in the Russian empire but not generally elsewhere.{{efn|Other exceptions are listed at [[adoption of the Gregorian calendar]].}} |
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==See also== |
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* [[Intercalation]] |
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==Notes== |
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{{notelist}} |
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* [[Calendar reform]] |
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==References== |
==References== |
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{{Reflist}} |
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* {{ cite book | title=A new system of practical astronomy: made plain and easy to those who have not studied mathematics : containing the elementary principles of the science, all the rules and tables necessary for making all the calculations for an almanac ... | first=Thomas | last=Spofford | publisher=Lemuel Gulliver | place=Boston | year=1835 | page=28 }} |
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==External links== |
==External links== |
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* [ |
* [https://aa.usno.navy.mil/faq/calendars An Introduction to Calendars courtesy of the United States Naval Observatory] {{Webarchive|url=https://web.archive.org/web/20190613115330/https://aa.usno.navy.mil/faq/docs/calendars.php |date=2019-06-13 }} |
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* [http://www.tondering.dk/claus/calendar.html Frequently Asked Questions about Calendars] |
* [https://web.archive.org/web/20051228123115/http://www.tondering.dk/claus/calendar.html Frequently Asked Questions about Calendars] |
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* [http://webexhibits.org/calendars/year-history.html History of Gregorian Calendar] |
* [http://webexhibits.org/calendars/year-history.html History of Gregorian Calendar] |
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[[Category:Units of time]] |
[[Category:Units of time]] |
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[[Category:Calendars]] |
[[Category:Calendars]] |
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[[Category:Julian calendar]] |
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[[Category:Gregorian calendar]] |
[[Category:Gregorian calendar]] |
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[[sv:Sekelskottår]] |
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{{time-stub}} |
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[[simple:Century leap year]] |
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Latest revision as of 19:35, 30 November 2024
 | This article needs additional citations for verification. (December 2020) |
A century leap year is a leap year in the Gregorian calendar that is evenly divisible by 400.[1]
Like all leap years, it has an extra day in February for a total of 366 days instead of 365. In the obsolete Julian calendar, all years that were divisible by 4, including end-of-century years, were considered leap years. The Julian rule, however, adds too many leap days (about 3 extra leap days in 400 years), which resulted in the calendar drifting gradually with respect to the astronomical seasons. To remedy this, Pope Gregory XIII introduced in 1582 a slightly modified version of the Julian calendar, the Gregorian calendar, where century years are leap years only if they are divisible by 400. This eliminates 3 of the 4 end-of-century years in a 400-year period. For example, the years 1600, 2000, 2400, and 2800 are century leap years since those numbers are evenly divisible by 400, while 1700, 1800, 1900, 2100, 2200, 2300, 2500, 2600, 2700, 2900, and 3000 are common years despite being evenly divisible by 4. This scheme brings the average length of the calendar year significantly closer to the astronomical length of the year, nearly eliminating the drift of the calendar against the seasons.
The Gregorian calendar was adopted by various countries at different times over several centuries. Dates prior to 1582 are generally recorded using the Julian calendar, and different countries have different conventions about how to record dates between 1582 and their adoption of the Gregorian calendar.[a] Consequently, for example, the year 1700 was a leap year in the British and Russian empires but not in most of the rest of Europe; 1800 and 1900 were still leap years in the Russian empire but not generally elsewhere.[b]
Notes
[edit]- ^ See, for example, Old Style and New Style dates.
- ^ Other exceptions are listed at adoption of the Gregorian calendar.
References
[edit]- ^ "Introduction to Calendars". United States Naval Observatory. n.d. Retrieved 9 May 2022.
Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is.
External links
[edit]- An Introduction to Calendars courtesy of the United States Naval Observatory Archived 2019-06-13 at the Wayback Machine
- Frequently Asked Questions about Calendars
- History of Gregorian Calendar
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