Leap Year Calculator
Check whether any year is a leap year, and how many days it has.
Not a leap year
No
365 days in this year
Comment ça marche
A year is a leap year if divisible by 4, except century years, which must be divisible by 400 (so 2000 was a leap year, but 1900 wasn't).
Why the century-year exception?
It corrects for the fact that a year is slightly less than 365.25 days — the extra rule keeps the calendar aligned with Earth's orbit over centuries.