Leap Year Calculator
Enter a year to find out whether it is a leap year and why.
Your calculation is performed in your browser.How it works
The calculator applies the standard Gregorian calendar leap year rule to the year you enter, and also searches outward to find the nearest leap years before and after it.
Formula & methodology
The Gregorian calendar adds a leap day (February 29) in most years divisible by 4. Century years are the exception, and only count if they are also divisible by 400. That is why 2000 was a leap year but 1900 was not.
Rule
Leap year = (Year mod 4 = 0) AND ((Year mod 100 ≠ 0) OR (Year mod 400 = 0))Days in year
Days in year = 366 if leap year, otherwise 365What each term means
- Remainder (mod)
- The remainder after division.
- Equal (=) and not equal (≠)
- Equal to / not equal to.
Examples
| Year | Result | Why |
|---|---|---|
| 2024 | Leap year | Divisible by 4, not by 100 |
| 1900 | Not a leap year | Divisible by 100 but not by 400 |
| 2000 | Leap year | Divisible by 400 |
| 2026 | Not a leap year | Not divisible by 4 |
Worked example
2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400).
Common uses
- —Checking whether a specific birth year, anniversary, or historical year was a leap year.
- —Finding the nearest leap years before or after a given year for planning or curiosity.
- —Verifying leap year status for calendar, scheduling, or software date-handling logic.
Important notes
- —The rule correctly separates common "divisible by 100" exceptions from the rarer "divisible by 400" exception, which is where most simple leap-year checks go wrong.