How do I know if a year is a leap year?

A year is a leap year if it is divisible by 4 — except for century years (like 1900), which must also be divisible by 400. So 2000 and 2024 are leap years, but 1900 and 2100 are not.

Why do leap years exist?

Earth takes about 365.2422 days to orbit the Sun. Adding a leap day (29 February) every four years keeps the calendar aligned with the seasons; the 100/400 rule fine-tunes the small remaining drift.

Leap Year Calculator

Free leap year calculator. Enter a year to see whether it's a leap year (366 days, February has 29), plus the next and previous leap years. Uses the Gregorian rule: divisible by 4, except centuries unless divisible by 400.

Check whether a year is a leap year and find the nearest leap years.

leap ⟺ (y mod 4 = 0 \land y mod 100 \neq = 0) \lor (y mod 400 = 0)

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