Year
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How this calculator works
The Earth takes about 365.2422 days to orbit the Sun, so a 365-day calendar drifts by nearly a day every four years. The Gregorian calendar corrects this by adding February 29 in years divisible by 4, but skipping century years unless they are divisible by 400. That is why 2000 was a leap year and 1900 was not.
Formula
- Leap year if divisible by 4
- Except century years (divisible by 100), which are not leap years
- Unless also divisible by 400, which are leap years
Worked example
The year 2028
- Year
- 2,028
Result2028 is a leap year
It is divisible by 4 and not a century year, so it has 366 days.
Frequently asked questions
Is 2100 a leap year?
No. It is divisible by 100 but not by 400, so it has 365 days.
Why do we have leap years?
To keep the calendar aligned with the seasons. Without them the calendar would drift about 24 days every century.
How often is there a leap year?
Usually every four years, with 97 leap years in every 400-year cycle.
More in Date & Time
Results are estimates based on the values you enter and the published method shown above. They do not replace professional medical, financial or legal advice. Method reviewed October 7, 2026. About this site