Leap Year Checker
A leap year occurs when an extra day (February 29) is added to the calendar to keep it synchronized with Earth's orbit around the Sun. The Gregorian calendar uses a three-part rule: a year is a leap year if it is divisible by 4, except for century years (ending in 00), which must be divisible by 400. This is why 2000 was a leap year but 1900 was not. Our leap year checker explains exactly which rule applies to any year you enter, helps you find the next upcoming leap year, browse past leap years, and list every leap year between two dates.
calendar_month Upcoming Leap Years
rule The 3-Part Rule
Divisible by 4
2024 ÷ 4 = 506 ✓ — base rule
Except century years
1900 ÷ 100 = 19 ✗ — exception
Unless divisible by 400
2000 ÷ 400 = 5 ✓ — override!
(y%4==0 && y%100!=0)
|| y%400==0
lightbulb Quick Facts
- •Leap year = 366 days (extra Feb 29)
- •Earth's year ≈ 365.2425 days
- •97 leap years every 400 years
- •2100, 2200, 2300 are NOT leap years
- •Next 400-year leap: 2400
The Formula
The Gregorian calendar corrects for the fact that Earth takes approximately 365.2425 days to orbit the Sun. Adding one day every 4 years slightly overcorrects, so century years (divisible by 100) skip the leap day, except every 400 years when the correction is needed again.
Leap year if: (year % 4 == 0 AND year % 100 ≠ 0) OR (year % 400 == 0)
lightbulb Variables Explained
tips_and_updates Pro Tips
The year 2000 was a leap year because it is divisible by 400 — this confused many early computers.
Leap years always fall on even years ending in 0, 4, 8, or (sometimes) 2 and 6.
February 29 birthdays are celebrated on February 28 or March 1 in non-leap years depending on local tradition.
The next century-year exception is 2100 — NOT a leap year despite being 4 years after 2096.
Adding a leap day every 4 years corrects for ~6 hours/year Earth takes beyond 365 days.
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All formulas verified against official standards.