What does 'leap year' mean?

It feels almost like science fiction to think that ten full days were removed from the calendar in the year 1582. But where does the phrase leap year come from? In 365-day years, known as common years, fixed dates advance one day in the week per year. read more

The term leap year gets its name from the fact that while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, in a leap year the day of the week will advance two days due to the year's extra day inserted at the end of February. read more

A leap year (also known as an intercalary year or bissextile year) is a calendar year containing one additional day (or, in the case of lunisolar calendars, a month) added to keep the calendar year synchronized with the astronomical or seasonal year. read more

As touched on above, a year that is divisible by 100, but not by 400, is not technically a leap year. Therefore 2000 was a leap year under the Gregorian calendar, as was 1600. But 1700, 1800 and 1900 were not. "There's a good reason behind it," Ian Stewart, emeritus professor of mathematics, told the BBC. read more