What is a Leap Year?
A leap year is a calendar year that contains an additional day (February 29th) added to keep the calendar year synchronized with the astronomical year or seasonal year.
The Leap Year Rule
To be a leap year, the year number must be divisible by four – except for end-of-century years, which must be divisible by 400. This means that the year 2000 was a leap year, although 1900 was not.