Leap year
A leap year is a calendar year in which an extra day is added to the Gregorian calendar, which is used by most of the world. A common year has 365 days, but a leap year has 366 days. The extra day, February 29, is added to the month of February. In a common year, February has 28 days, but in a leap year it has 29 days. The extra day, called a leap day, occurs on the same day of the week as the first day of the month, February 1. Additionally, a leap year does not begin and end on the same day of the week, as a common year does.