Century leap year: Difference between revisions
Made explanation more explicit, to avoid misinterpretation (I noticed the confusion when a colleague incorrectly cited the previous version of this page as evidence that 0200 would have been a leap year.) Added that it was introduced in 1582. |
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Starting with 1600, every year that is [[divisible]] by 400 is an '''end-of-century [[leap year]]''' (often referred to as a '''century leap year'''), qualifying for the [[Intercalation (timekeeping)|intercalation]] of [[February 29]], the same as other leap years. End-of-century years that are ''not'' divisible by 400 are [[common year]]s. For example, The years 1600, 2000, and 2400 are end-of-century leap years, while 1700, 1800, 1900, 2100, 2200, and 2300 are common years despite being end-of-century years. Leap years divisible by 400 always start on a Saturday; thus the leap day February 29 in those years always falls on a Tuesday. |
Starting with 1600, every year that is [[divisible]] by 400 is an '''end-of-century [[leap year]]''' (often referred to as a '''century leap year'''), qualifying for the [[Intercalation (timekeeping)|intercalation]] of [[February 29]], the same as other leap years. End-of-century years that are ''not'' divisible by 400 are [[common year]]s (''not'' leap years). For example, The years 1600, 2000, and 2400 are end-of-century leap years, while 1700, 1800, 1900, 2100, 2200, and 2300 are common years despite being end-of-century years. Leap years divisible by 400 always start on a Saturday; thus the leap day February 29 in those years always falls on a Tuesday. |
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The end-of-century year "divisible by 400" rule, introduced in 1582 by the [[Gregorian calendar]], yields an average year that tracks the annual revolution period of the earth more closely than the older [[Julian calendar]], which provided for a leap year every four years. Thus ''every'' end-of-century year is a leap year in the Julian calendar. This adds too many leap days, causing the Julian calendar to drift gradually with respect to the astronomical seasons. Over time, natural events such as the spring equinox began to occur earlier and earlier in the Julian calendar. |
The end-of-century year "divisible by 400" rule, introduced in 1582 by the [[Gregorian calendar]], yields an average year that tracks the annual revolution period of the earth more closely than the older [[Julian calendar]], which provided for a leap year every four years. Thus ''every'' end-of-century year is a leap year in the Julian calendar. This adds too many leap days, causing the Julian calendar to drift gradually with respect to the astronomical seasons. Over time, natural events such as the spring equinox began to occur earlier and earlier in the Julian calendar. |
Revision as of 17:03, 31 January 2017
Starting with 1600, every year that is divisible by 400 is an end-of-century leap year (often referred to as a century leap year), qualifying for the intercalation of February 29, the same as other leap years. End-of-century years that are not divisible by 400 are common years (not leap years). For example, The years 1600, 2000, and 2400 are end-of-century leap years, while 1700, 1800, 1900, 2100, 2200, and 2300 are common years despite being end-of-century years. Leap years divisible by 400 always start on a Saturday; thus the leap day February 29 in those years always falls on a Tuesday.
The end-of-century year "divisible by 400" rule, introduced in 1582 by the Gregorian calendar, yields an average year that tracks the annual revolution period of the earth more closely than the older Julian calendar, which provided for a leap year every four years. Thus every end-of-century year is a leap year in the Julian calendar. This adds too many leap days, causing the Julian calendar to drift gradually with respect to the astronomical seasons. Over time, natural events such as the spring equinox began to occur earlier and earlier in the Julian calendar.
See also
Sources
- Spofford, Thomas (1835). 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 …. Boston: Lemuel Gulliver. p. 28.