Why is the century year not considered as a leap year?

There is a leap year every year whose number is perfectly divisible by four - except for years which are both divisible by 100 and not divisible by 400. The second part of the rule effects century years. For example; the century years 1600 and 2000 are leap years, but the century years 1700, 1800, and 1900 are not. read more

Leap years were created to keep our calendar in sync with the seasons. The problem is that it takes the Earth approximately 365.25 rotations to make one lap around the background stars (this is called a Tropical Year). So a year should not be 365 days, it should be approximately 365 and 1/4 days. read more

Such years, in the Gregorian calendar, which is used now, are NOT leap years except for integer multiples if 400. So 1900 was not a leap year, 2000 was, and 2100 will not. The Julian calendar assumed the year was exactly 365_1/4 days long, so in it any year which is integer multiple of 4, including all century years, is a leap year. read more

Century years (divisible by 100) that are not divisible by 400 are common years (with 365 days) and not leap years. For example, the years 1600, 2000, and 2400 are century leap years since those numbers are divisible by 400, while 1700, 1800, 1900, 2100, 2200, and 2300 are common years despite being divisible by 4. read more