Leap Year Checker
Check whether a year is a leap year, and see upcoming leap years.
2024 is a leap year.
Next leap years: 2028, 2032, 2036
About this tool
A leap year has 366 days instead of 365, with an extra day, February 29, added to keep the calendar year synchronized with Earth's actual orbit around the Sun — which takes about 365.2422 days, not a clean 365.
This tool checks any year using the standard Gregorian calendar rule: a year is a leap year if it's divisible by 4, except century years, which must be divisible by 400. This refinement — added when the Gregorian calendar replaced the Julian calendar in 1582 — is why 2000 was a leap year but 1900 and 2100 are not.
Without leap years, the calendar would drift by about a day every four years, and after a few centuries the seasons would fall in completely different calendar months than they do today.
Formula
Leap year if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
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Frequently asked questions
- What makes a year a leap year?
- A year is a leap year if it is divisible by 4, except for century years (those ending in 00), which must also be divisible by 400 to be a leap year. That's why 2000 was a leap year but 1900 and 2100 are not.
- Why do leap years exist?
- Earth's orbit around the Sun takes about 365.2422 days, not exactly 365. Without an extra day roughly every 4 years, the calendar would slowly drift out of sync with the seasons — after a few centuries, Northern Hemisphere "summer" months would gradually shift toward winter.
- Why isn't every 4th year a leap year, without exception?
- Adding a day every 4 years slightly overcorrects, since a year is close to but not exactly 365.25 days. Skipping the leap day in century years not divisible by 400 (like 1700, 1800, 1900) fine-tunes the calendar to stay accurate to within about 26 seconds per year.
- What happens to February 29 birthdays in a non-leap year?
- People born on February 29 ("leaplings") typically celebrate on February 28 or March 1 in non-leap years. Some countries have specific legal rules for when age-related milestones officially apply in those years.