Century leap year

A century leap year is a year in the Gregorian calendar that is evenly divisible by 400 and is thus a leap year.

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 introduced in 1582, but was adopted by various countries at different times over several centuries. Dates prior to 1582 are generally calculated using the Julian calendar, and different countries have different conventions about how to record dates between 1582 and their adoption of the Gregorian calendar. The years 1916, 1944, 1972, and the century leap year 2000, are followed by other leap years starting on Saturday 2028, 2056, and 2084, are followed by 2124, 2152, 2180, 2220, 2448, 2276, 2316, 2344, 2372, and the century leap year 2400, along with 2428, 2456, 2484, 2524, 2552, 2580, 2620, 2648, and 2676, along with 2716, 2744, 2772, and 2800, along with 2828, 2856, 2884, 2924, 2952, 2980, and others like 3020, 3048, 3076, 3116, 3144, 3172, and 3200 as a century leap year, but the century leap year has followed 3228, 3256, 3284, 3324, 3352, 3380, 3420, 3448, 3476, 3516, 3544, 3572, and the century leap year of 3600, along with 3628, 3656, 3684, 3724, 3752, 3780, 3820, 3848, 3876, 3916, 3944, 3972, and 4000 as our other century leap year, but 4028, 4856, and 4084 are regular Saturday leap years, as well as 4124, 4152, and 4180, and 4220, 4248, and 4276, along with 4316, 4344, 4372, and the century leap year 2400, like 4428, 4456, 4484, 4524, 4552, 4580, 4620, 4648, 4676, 4716, 4744, 4772, 4800 the century leap year, 4828, 4856, 4884, 4924, 4952, and 4980. Other century leap years go 5020, 5048, 5076, 5116, 5144, 5172, 5200, the century leap year before 5228, 5256, 5284, 5324, 5352, 5380, 5420, 5448, 5476, 5516, 5544, 5572, century leap year 5600, 5628, 5656, 5684, 5724, 5752, 5780, 5820, 5848, 5876, 5916, 5944, 5972, and the final century leap year of 6000. These century leap years appear at the end of other centuries. Others appear in other millenniums. 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 elsewhere.

External links

• 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