Leap years have 366 days (29

Any year that is divisible by 4 but not by 100 is a leap year. If a year is divisible by 400 then it is also a leap year.

So in short any year that is divisible by 4 is a leap year, unless it is divisible by 100, in which case it must also be divisible by 400 for it to be a leap year. Example: 1996 and 2000 were leap years, but 1900 was not. days in February).