How to Use the Leap Year Checker
February 29th rolls around every four years, but figuring out whether a given year actually qualifies isn't always as simple as "divisible by 4." Century years follow a different rule, which trips up the common shortcut. Just enter a year, and this calculator applies the exact Gregorian calendar rule to tell you whether it's a leap year, how many days February has that year, and when the next leap year will occur.
The rule works in three steps. First, a year divisible by 4 is a leap year candidate. But if it's also divisible by 100, it reverts to a common year — unless it's additionally divisible by 400, in which case it's a leap year after all. That's why 1900 was a common year while 2000 was a leap year, and why 2100 will be a common year too. This extra layer of rules exists because Earth's orbit takes about 365.2422 days, not a clean 365, so the calendar needs periodic correction to stay aligned with the seasons.
If you were born on February 29th, you've probably wondered which date to celebrate in a common year — that and other common leap year questions are answered in the FAQ below.
Frequently Asked Questions
Under the Gregorian calendar, a year is a leap year if it's divisible by 4. However, years divisible by 100 are not leap years, unless they're also divisible by 400, in which case they are.
1900 is divisible by 4 and by 100, but not by 400, so it's not a leap year. 2000, on the other hand, is divisible by 400, so it is a leap year. This exception rule skips a leap year roughly once every 100 years.
It takes Earth about 365.2422 days to orbit the sun, not exactly 365. Adding one extra day (February 29) every 4 years keeps the calendar synced with that leftover 0.2422 days per year.