Rules For Leap Year Math

Identify the year you want to check.

Rules for leap year math. Leap years occur every 4 years. Now if a year is divisible by 100 we are not sure if it is a leap year yet. Except that every 100 years special rules apply. We need to test if it is divisible by 400.

So 1700 1800 and 1900 are not leap years but 1600 and 2000 are leap years. Every year that is exactly divisible by four is a leap year except for years that are exactly divisible by 100 but these centurial years are leap years if they are exactly divisible by 400. 2020 is a leap year and so is 2024. The rule used to determine whether a year is a common year or a leap year as described by the united states naval observatory is as follows.

It has 366 days instead of the normal 365 days. A year containing an extra day. Dividing the year by 4 will result in a whole number with no remainder if. The extra day is added in february which has 29 days instead of the normal 28 days.

So another rule says that every 400 years is a leap year again. Confirm the number isn t evenly divisible by. This gets us 365 2425 days per year 1 day regained every 400 years 0 0025 days per year which is close enough to 365 242375 not to matter much. Closer but still not accurate enough.

See if the number is evenly divisible by 4. For example 1900 was not a leap year but 2000 was. The year 2000 was a leap year because even though it is divisible by 100 it s also. If it is divisible by 400 then it is a leap year otherwise it is not.

So 1996 was a leap year but 1997 1998 and 1999 were not. The year is divisible by 400 then it is a leap year. So every 100 years we don t have a leap year and that gets us 365 24 days per year 1 day less in 100 year 0 01 days per year.