Leap year calculator
Check whether a year is a leap year and find the nearest ones.
Fill in the fields and the result will appear here automatically.
Applies the Gregorian rule: a year divisible by four is a leap year, except century years, which must also be divisible by four hundred. That is why 1900 was ordinary and 2000 was not.
How it works
Formula and logic
The Gregorian rule requires divisibility by 4 and either non-divisibility by 100 or divisibility by 400. It produces 97 leap years per 400 years. Enter a whole year; zero, fractions and malformed values are rejected. Nearby leap years are strictly before and after the chosen year, so 2024 is followed by 2028. Early years use the same mathematical rule without reconstructing any country’s historical calendar. A leap second belongs to timekeeping and does not change the days in February.
Example
2024 is a leap year, 1900 was not, and 2000 was — because it divides by 400.
Fields and units
- Year — unitless. Whole numbers within the displayed range; invalid entries are not clamped to a boundary.
How to use
- — Enter the year.
- — Read the answer.
- — Check the nearest leap years if you need them.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- NASA, section 2.1: Gregorian leap rule and proleptic dates; anniversary and shift conventions belong to this model
- Limitation
- Early years use the same mathematical rule without reconstructing any country’s historical calendar. A leap second belongs to timekeeping and does not change the days in February.
FAQ
Why is the century exception needed?
A tropical year is about 365.2422 days, slightly less than 365.25. Dropping three leap days every four centuries keeps the calendar aligned with the seasons.
Was 1900 a leap year?
No. It divides by 100 but not by 400, so February had 28 days.
How often does a leap year occur?
Every four years, apart from those century exceptions — 97 leap years in every 400.
Does the rule work for old dates?
The calculator applies the Gregorian rule to early years too. It does not reconstruct when a country changed from the Julian calendar, so historical documents need a separate calendar check.