Leap Year Checker
NewCheck whether any year is a leap year under the Gregorian calendar rule, with a plain-English explanation of why, plus a list of nearby leap years.
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Nearby leap years
Frequently Asked Questions
What is the exact rule for determining a leap year?
A year is a leap year if it's divisible by 4, except century years (divisible by 100), which are only leap years if they're also divisible by 400 — that's the full Gregorian calendar rule, and it's why 2000 was a leap year but 1900 and 2100 are not.
Why does this century-year exception exist at all?
A true solar year is about 365.2422 days, slightly less than the 365.25 days implied by a simple "every 4th year" rule — dropping 3 leap years every 400 years (the century exception, undone once every 4 centuries) brings the calendar's average year length much closer to the actual solar year, keeping seasonal drift extremely small over long timescales.
Does this tool account for years before the Gregorian calendar was adopted?
No — it applies the modern Gregorian rule uniformly to any year you enter; it doesn't model the older Julian calendar (which used a simpler "every 4th year, no exceptions" rule) or the transition period, which varied by country.
Can I check very large or very old years?
Yes — the year input accepts any positive integer, and the same divisibility rule is applied mathematically regardless of how far in the past or future the year is.
What do the "nearby leap years" chips show?
Up to four leap years immediately before and after your entered year, so you can quickly see the surrounding pattern (leap years are usually 4 years apart, except around non-leap century years where the gap stretches to 8 years).