Leap Year Checker
Is this a leap year?
The answer, the rule that produced it, the next and previous leap years, and the century exceptions that catch people out.
Questions people ask
The things that come up about leap year checkers, answered plainly.
What is the leap year rule?
A year is a leap year if it divides by 4, except that century years must also divide by 400. So 2024 is, 1900 was not, and 2000 was. That last exception is what most hand-written checks get wrong.
Why is 2100 not a leap year?
Because it divides by 100 but not by 400. The rule exists because the tropical year is 365.2422 days, not 365.25 — adding a leap day every four years overshoots by about 11 minutes a year, and skipping three centuries in every four corrects it to within a day per 3,000 years.
How many leap years are there in 400 years?
Ninety-seven. That gives an average year of 365.2425 days, which is the Gregorian calendar's whole purpose.
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