Why is 1900 not a leap year but 2000 is?

Both are divisible by 100, which normally disqualifies a year from being a leap year — but years divisible by 400 are an exception and remain leap years. 2000 is divisible by 400; 1900 is not.

How many days are in a leap year?

A leap year has 366 days, with the extra day added as February 29, compared with 365 days in a common year.

Age, Date & Calendar

Leap Year Calculator

Enter a year to find out whether it is a leap year and why.

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Enter a year to check whether it is a leap year.

How it works

The calculator applies the standard Gregorian calendar leap year rule to the year you enter, and also searches outward to find the nearest leap years before and after it.

Formula & methodology

A year is a leap year if it is divisible by 4, unless it is also divisible by 100 — in which case it is only a leap year if it is also divisible by 400.

Worked example

2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400).

Important notes

—The rule correctly separates common "divisible by 100" exceptions from the rarer "divisible by 400" exception, which is where most simple leap-year checks go wrong.