On This Day in History: Leap Year Day
In 2012 we add one day more day to the year, Feb. 29, to bring our calendar more nearly into accord with the seasons.
Under the Julian calendar, every fourth year was a leap year, on the assumption that it took the Earth 365.25 days to orbit the sun. However, the Earth’s orbital period is actually 365.24219 days. Over the more than 1,600 years that the Julian calendar was used the calendar got out of sync with the seasons. The Gregorian calendar made just one small change: a leap day is added to the calendar once every four years except for century years which are not exactly divisible by 400. Since 2000 was divisible by 400, it was a leap year, 1900 was not. The next leap year will be 2016.
Common Years and Leap Years