Leap Year Checker

Check if any year is a leap year free online using the real Gregorian calendar rule. See the exact reasoning, plus a list of upcoming leap years.

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How to Use This Tool

1
Enter any yearPast, current, or future
2
See the result and reasoningWhich rule determined the answer
3
Check the next few leap yearsListed for quick reference

Three Rules, Not Just One

"Divisible by 4" is only the starting point -- the real Gregorian rule adds a century exception (not a leap year if divisible by 100) and then an exception to that exception (it IS a leap year if also divisible by 400). This calculator applies the complete three-part rule and shows exactly which part determined your answer.

Why the Correction Exists

A tropical year is approximately 365.2422 days, not precisely 365.25, so a simple every-4-years rule would overcorrect slightly, accumulating drift over centuries. The century exception (and its own exception at every 400 years) keeps the calendar much more closely aligned with the actual solar year over long periods.

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Frequently Asked Questions

A year is a leap year if it's divisible by 4, EXCEPT years divisible by 100 are not leap years, UNLESS they're also divisible by 400, in which case they are. This three-part rule, not just simple divisibility by 4, is the real Gregorian calendar standard.
A simple every-4-years rule would add slightly too many leap days over centuries, since a tropical year is approximately 365.2422 days, not exactly 365.25. The century exception corrects for this small accumulated drift.
2000 is divisible by 400 (the exception-to-the-exception), making it a leap year despite being divisible by 100. 1900 is divisible by 100 but not by 400, making it NOT a leap year -- exactly the distinction the three-part rule is designed to capture.
Software handling dates, financial calculations involving daily interest, and calendar-dependent scheduling all need correct leap year handling -- getting it wrong produces real, sometimes subtle bugs in date arithmetic.
Roughly every 4 years, but with the century exception removing 3 leap years every 400 years, the actual average is 97 leap years per 400 years rather than a perfectly even 100.
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