Leap Year Checker
Check whether a year is a leap year, and list the next few leap years from that point. Uses the Gregorian rule: divisible by 4, except century years not divisible by 400.
Inputs
Verdict
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Next 5 leap years
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Length of this year
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Days in February
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About Leap Year Checker
The rule
A year is a leap year if it is divisible by 4 — except for century years (1700, 1800, 1900), which must also be divisible by 400. So 2000 was a leap year, but 1900 wasn’t and 2100 won’t be.
Why the exception?
The solar year is about 365.2422 days. Adding a day every 4 years overshoots slightly; skipping 3 of every 4 century leap days corrects most of the drift.
When was it adopted?
The Gregorian calendar was introduced in 1582 by Pope Gregory XIII. Different countries adopted it on different dates — Britain in 1752, Russia in 1918. Before that, the Julian calendar used a simpler "every 4 years" rule.