How it works
A year is a leap year if it's divisible by 4 — except century years (divisible by 100), which are only leap years if also divisible by 400. That's why 2000 was a leap year but 1900 and 2100 are not.
Leap Year Checker
Check if a year is a leap year, plus nearby leap years.
Interactive calculator
This calculator becomes interactive when JavaScript is available. The page still provides its method, limits and related tools without JavaScript.
Result classification
Mathematically exact. The result uses deterministic calendar or arithmetic rules on the values you enter. Dates are normalized before calculation, and invalid inputs are rejected.
Limitations
Exact for the stated rule and valid inputs; it does not decide legal, medical, contractual or policy questions.
Frequently asked questions
Why isn't 1900 a leap year if it's divisible by 4?
Century years need to be divisible by 400, not just 100, to stay leap years — this correction keeps the calendar aligned with Earth's orbit over long spans of time.
Practical guide
Reviewed 27 July 2026How to use the Leap Year Checker
- Enter the known values.Use the date, time, place or duration requested above.
- Check the assumptions.Confirm time zone, weekend, inclusion and rounding choices when shown.
- Read and reuse the result.Copy, share or continue to a related tool without retyping unnecessary information.
Common uses
The Leap Year Checker is useful for reporting periods, school terms, publishing and recurring schedules.
Edge cases to check
Pay particular attention to ISO week-year boundaries, leap years and different first-day-of-week customs.