Leap Year Checker

Is a given year a leap year? Apply the Gregorian rule with a step-by-step explanation.

Inputs

Any positive 4-digit year.

Result

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How to use this calculator

  • Enter a year.
  • Read whether it is a leap year along with the divisibility steps and the previous/next leap year.

About this calculator

A leap year has 366 days instead of 365 to keep the calendar synchronized with the solar year. The Gregorian rule, which has been in use since 1582, says: every year divisible by 4 is a leap year, except century years (divisible by 100), unless those are also divisible by 400. So 2000 was a leap year but 1900 was not, and 2100 will not be.

Frequently asked

Why is the rule so complicated?+
The solar year is about 365.2425 days, not exactly 365.25. Adding a leap day every 4 years (the Julian rule) over-corrects by about 3 days every 400 years. The Gregorian fix removes 3 of every 4 century leap years, bringing the average back down to 365.2425 days.
Was 2000 a leap year?+
Yes — 2000 is divisible by 400, so it overrides the "century years are not leap" exception. It was the first time that override mattered since the Gregorian calendar was introduced.
Is 2100 a leap year?+
No — 2100 is divisible by 100 but not by 400, so the exception applies and 2100 has only 365 days.
How often does Feb 29 occur?+
Roughly once every 4 years, but the century-year exception means there are 97 leap years in every 400-year cycle (not 100). Average: one Feb 29 every 4.124 years.
Can a year be a leap year in some calendars and not others?+
Yes — different calendars (Julian, Hebrew, Islamic, Hindu) have different rules. This calculator only handles the Gregorian (proleptic) rule, which is what almost all civil calendars use today.

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