Determine whether a year is a leap year. Enter any year to see its leap-year status, the number of days in the year and the next leap year.
Enter a year. The calculator checks the leap-year rules (divisible by 4, but not by 100 unless also by 400), tells you whether it's a leap year, how many days it has and when the next leap year falls.
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A leap year calculator checks whether a year has an extra day (29 February). Leap years keep our calendar aligned with Earth's orbit around the Sun.
So 2000 was a leap year, 1900 was not, and 2100 will not be.
A year is about 365.2425 days long. Without the extra day every four years, the calendar would drift out of step with the seasons over time.
Adding a leap day every four years slightly overshoots, so years divisible by 100 skip a leap year — unless they're also divisible by 400, which keeps things accurate over centuries.