Type any year and find out instantly whether it has 366 days, which rule decided it, and when the next and previous leap years fall.
| Year | Leap year? | Days | Why |
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Nothing is sent anywhere — the rule is applied right here in the page.
Type a year and get a clear yes or no along with the reasoning behind it.
See exactly which part of the divisible-by-4, 100 and 400 rule decided the outcome.
A table of surrounding years makes century exceptions easy to spot.
Leap years follow three stacked rules, and the checker shows you which one applied.
A solar year is not a whole number of days, so any calendar that ignores the remainder eventually drifts out of step with the seasons. The Julian calendar added a day every four years, which slightly overcorrected. The Gregorian reform of 1582 removed three leap days every four centuries by skipping most century years, and that is the calendar almost the whole world uses today.
Divisible by 4 makes a leap year, divisible by 100 cancels it, and divisible by 400 restores it. Each rule overrides the one before.
It is divisible by 100 but not by 400, so the century exception applied. This caught out a surprising amount of early software.
Leap seconds adjust for irregularities in Earth's rotation, not its orbit, and are announced only a few months in advance.
Dates before the Gregorian reform followed the Julian rule, where every fourth year was a leap year with no exceptions. This tool applies the Gregorian rule throughout.
Common questions about the rule, its exceptions and February 29.
A year is a leap year if it is divisible by 4, except that years divisible by 100 are not, unless they are also divisible by 400. So 2024 is a leap year, 1900 was not, and 2000 was.
The Earth takes about 365.2422 days to orbit the Sun. Without an extra day roughly every four years, the calendar would drift about six hours per year and the seasons would slowly slide out of place.
Yes. It is divisible by 400, which overrides the century exception. The next century year to be skipped is 2100.
Leaplings typically celebrate on 28 February or 1 March in common years. Legal treatment varies by country, and some jurisdictions define the legal birthday as 1 March.
The 400-year cycle averages 365.2425 days per year against a true tropical year of about 365.2422, an error of roughly one day every 3,200 years.