Leap Year Calculator

The leap year calculator tells you whether any year is a leap year — one with 366 days and a 29 February — and explains why. Enter a year and it returns a clear yes or no, the rule that decides it, and the next leap year to come.

Leap years exist to keep our calendar aligned with the Earth's orbit. A solar year is about 365.2422 days, so a fixed 365-day calendar would slowly drift out of step with the seasons. Adding an extra day almost every four years corrects most of that drift.

The rule has three parts. A year is a leap year if it is divisible by 4 — except years divisible by 100, which are not leap years, unless they are also divisible by 400, which are. That is why 1900 was a common year but 2000 was a leap year: both are divisible by 100, but only 2000 is divisible by 400. This 400-year refinement keeps the calendar accurate to within a day for thousands of years.

To use the calculator, type a year and press Check the year. You will see whether it is a leap year, the specific rule that applies, and the next leap year after it. It works for any year, past or future, so you can check a historical date or plan around a future 29 February.

People use this to confirm whether a birthday or anniversary falls in a leap year, to check date logic in spreadsheets and code, and simply to settle the recurring question of why some Februaries have an extra day.

A year is a leap year when it is divisible by 4 and not by 100, or when it is divisible by 400. In short: divisible by 4 → leap, unless divisible by 100 → common, unless also divisible by 400 → leap.