Century leap year

In the Gregorian calendar, an end-of-century leap year (often referred to as a century leap year) is a year that is exactly divisible by 400 and, as with every other leap year, qualifies for the intercalation of February 29. End-of-century years that are not divisible by exactly 400 are common years. The years 2000 and 2400 for example, are end-of-century leap years in a century with 36,525 days, while 1700, 1800, 1900, 2100, 2200, 2300, 2500, and 2600 are common years in a century with 36,524 days. Leap years divisible by 400 always start on a Saturday, and thus the resulting upcoming February 29 (the leap day) is always on a Tuesday.

The end-of-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 at four year intervals. Over time, the Julian practice resulted in too many leap days being added to the calendar, thus causing it to gradually drift with respect to the astronomical seasons of the years (and natural events, such as the spring equinox, to occur earlier and earlier in the calendar).

See also

• Calendar reform

External links

• An Introduction to Calendars courtesy of the United States Naval Observatory
• Frequently Asked Questions about Calendars
• History of Gregorian Calendar