Check a year
- Enter a whole Gregorian year from 1 to 9,999.
- Calculate whether it is leap or common, with year and February day counts.
- Review the next later leap year and copy or download the result.
Gregorian rule and examples
A year is leap when it is divisible by 4, except century years must also be divisible by 400. The U.S. Naval Observatory explains this rule and why the 400-year cycle contains 97 leap years.
2024 is leap: 366 days, with 29 in February. 1900 and 2100 are common years despite being divisible by 4, because they are century years not divisible by 400. 2000 and 2400 are leap years. 2023 is common: 365 days and 28 in February.
The next leap year is strictly later than your input. After 2024 it is 2028; after 2096 it is 2104, because 2100 is not leap.
Limits and privacy
Whole years 1–9,999; no year zero, BCE years or other calendar systems. Gregorian rules are applied consistently, including before historical adoption; this does not reconstruct historical regional calendars. If the next leap year is beyond 9,999, it is labeled unavailable.
Inputs stay in browser memory without uploads or saved years. CSV includes year, leap/common status, day counts, next year and the applied rule code. Reset restores the example year and clears results. Undo action restores the previous entered year before a shortcut, example, nearby-year choice, next-year jump or Reset. Check again after restoring; editing starts a new state.
Is every fourth year a leap year?
Century exceptions mean that simple rule is incomplete. Divisibility by 400 determines whether a century year is leap.
Is this about leap seconds?
No. Leap days and leap seconds are different systems. This checker only applies the Gregorian calendar’s year-length rule.