Check whether a given year is a leap year under the Gregorian calendar.
How it works
A year is a leap year if it’s divisible by 4, except century years must also be divisible by 400. 2024 is a leap year (divisible by 4, not a century year); 1900 is not (divisible by 100 but not 400); 2000 is (divisible by 400).
What this does not include
This uses the modern Gregorian calendar’s rule. It doesn’t account for the older Julian calendar’s simpler every-4-years rule, which some historical dates were recorded under before the Gregorian reform.
How to use this calculator
- Enter a year.
A worked example
2024: divisible by 4 and not a century year → leap year.
1900: divisible by 4, but a century year not divisible by 400 → not a leap year — a common exception people forget.
2000: divisible by 4 and by 400 → leap year, despite being a century year.
What the variables mean
| Variable | Meaning |
|---|---|
| Year | The calendar year being checked |
Edge cases worth knowing
Century years follow a special rule most people don’t know. A year divisible by 100 is only a leap year if it’s also divisible by 400 — which is why 1900 wasn’t a leap year but 2000 was, even though both are divisible by 4.
This three-part rule (divisible by 4, not by 100 unless also by 400) keeps the calendar aligned with Earth’s actual orbital period, which isn’t exactly 365.25 days.
Why do century years need a special rule?
A pure every-4-years rule would make the calendar drift from the actual solar year by about 3 days every 400 years — the century exception corrects most of that drift by skipping 3 leap years per 400-year cycle.
Why is 2000 a leap year but 1900 wasn’t?
2000 is divisible by 400 (2000 ÷ 400 = 5 exactly), which makes it a leap year despite being a century year; 1900 is divisible by 100 but not by 400, so it fails the century exception and isn’t one.
How often does a leap year actually occur?
On average, once every 4 years, minus the century exceptions — about 97 leap years occur every 400 years under the Gregorian rule.
