Check if a year is a leap year, and see the next and previous ones — free and instant.
A year is a leap year — with an extra day, February 29th — if it's divisible by 4, except century years (divisible by 100), which are only leap years if also divisible by 400. This is why 2000 was a leap year but 1900 and 2100 are not, even though all three are divisible by 100.
This rule exists because Earth's orbit doesn't take exactly 365 days — it takes about 365.2422 days, and adding a leap day roughly every 4 years (skipping most century years) keeps the calendar closely aligned with the actual seasons over long periods.
Century years are a special exception — divisible by 100 but not by 400 — and 1900 fails that stricter test, even though it passes the simpler divisible-by-4 rule.
Yes — it’s divisible by 400, which overrides the century-year exception.
2400 — it’s divisible by 400. 2100, 2200, and 2300 will all be ordinary (non-leap) years despite being divisible by 4.