How to calculate leap year? What are the rules?

1, non-integer centenary: leap year is divisible by 4. (For example, 2004 is a leap year, and 200 1 is not. )

2, the whole hundred years: leap years can be divisible by 400. (For example, 2000 is a leap year, 1900 is not. )

3. For years with large numbers: if this year is divisible by 3200, it is not a leap year, but if it is divisible by 172800, it is a leap year. For example, 172800 is a leap year, and 86400 is not (because it can be divisible by 3200, but not by 172800). (This is calculated according to 365 days, 5 hours, 48 minutes and 45.5 seconds)

Extended data:

Reasons for leap years

The usual explanation is that there are many days, hours and minutes in a year, and there is still a surplus after taking an integer of 365 days. After accumulating to one day (24 hours), one more day is added, and the year with one more day is a leap year. This explanation just tells everyone how to calculate, which is artificially set.

The most fundamental reason is that the cycle of the earth's orbit around the sun is 365 days, 5 hours, 48 minutes and 46 seconds (365 days +09 days), which is the tropic of cancer. The Gregorian calendar has an average of only 365 days a year, which is about 0.2422 days shorter than the tropical year, and the remaining time is about one day every four years. So 1 day is added at the end of February of the fourth year, making the length of a year 366 days, and this year is a leap year.

The current Gregorian calendar has 97 leap years every 400 years. According to a leap year every four years, it will count as 0.0078 days per year on average, so after 400 years, it will count as 3 days.

So every 400 years, three leap years will be reduced. Therefore, the Gregorian calendar stipulates that when the year is a whole hundred, it must be a multiple of 400 to be a leap year; It is not a century year with multiples of 400, and even a multiple of 4 is not a leap year.