Leap Year Checker

Is it a leap year?

A leap year has 366 days instead of 365, with an extra day, 29 February. Enter a year and the checker answers right away, and explains why. The list below it shows every leap year between two years you choose, which is handy for planning events, contracts or software tests across a long span.

The Gregorian calendar rule has three steps. A year divisible by 4 is a leap year. However, a year divisible by 100 is not a leap year, unless it is also divisible by 400, in which case it is. So 2024 and 2028 are leap years, 1900 and 2100 are not, and 2000 was.

Why leap years exist

The Earth takes about 365.2422 days to orbit the Sun. A calendar of exactly 365 days would drift against the seasons by almost a day every four years. Adding a leap day roughly every four years corrects most of the drift, and skipping it in most century years corrects the rest. The result keeps the calendar within about a day of the seasons over thousands of years.

People born on 29 February are sometimes called leaplings. They celebrate in non-leap years on 28 February or 1 March depending on local custom and law.

Using the range list

Choose a start and end year to list every leap year between them along with the count. Ranges are capped at about five thousand years for performance. If you need to know how many days remain until a date, try the days-until tool. The checker runs locally in your browser with no data sent anywhere.

Software developers often need these rules to validate dates or calculate ages correctly. A common bug is checking only divisibility by 4, which gives the wrong answer for years like 1900 and 2100. This tool follows the full Gregorian rule.