Leap Year Calculator
Check whether a year is a leap year.
Find out if a year has 366 days.
The math behind it
A year is a leap year if divisible by 4 — but century years must also be divisible by 400 (so 1900 wasn't, 2000 was).
Worked example
2024 → leap year (366 days).
FAQ
Why the 400 rule?
It corrects the small over-count of the simple every-4-years rule.