Leap Year Calculator
Is a year a leap year? Check any year, see the leap years around it and the rule that decides — every 4 years, except centuries not divisible by 400.
A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400: 2024 yes, 2100 no, 2000 yes.
How the leap year calculator works
A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400: 2024 yes, 2100 no, 2000 yes. This keeps the calendar year within a day of the solar year for thousands of years.
Formula: leap ⇔ (y mod 4 = 0 and y mod 100 ≠ 0) or y mod 400 = 0
Worked examples
| Inputs | Leap year? | Note |
|---|---|---|
| 2024 | Yes — 2024 is a leap year | yes |
| 2100 | No — 2100 is not a leap year | no — a century not divisible by 400 |
| 2000 | Yes — 2000 is a leap year | yes |
FAQFrequently asked questions
Why do we have leap years?
The solar year is about 365.2422 days; adding a day roughly every four years keeps the seasons in place.
Why isn't 2100 a leap year?
Every four years overshoots slightly, so three century years in every four are skipped.
How accurate is the Gregorian calendar?
About one day in 3,000 years.
Is 2026 a leap year?
No; the next is 2028.
What day is 29 February 2028?
A Tuesday.
Where these figures come from
- ISO 8601 — Date and time — Representations for information interchange — the yyyy-mm-dd format and the week-numbering rules used here
- US Naval Observatory — Calendars — the Gregorian leap-year rule
- US Office of Personnel Management — federal holidays — federal holidays (not applied here)
Last checked: September 2026. The Gregorian calendar rules do not change; working-day counts exclude Saturdays and Sundays only.