Leap Year Calculator

How does this calculator work?

A Gregorian leap year is divisible by four, except century years must also be divisible by 400. Therefore 2000 was a leap year, 1900 was not, and 2028 will be one.

Quick example

The year 2028 is divisible by four, so February has 29 days. The year 2100 is divisible by 100 but not 400, so it is not a leap year.

Frequently asked questions

Is every fourth year a leap year?

Almost. Century years ending in 00 must be divisible by 400.

Does this apply to dates before the Gregorian calendar existed?

It applies Gregorian rules proleptically. Historic calendars varied across countries.