How to use it
- Enter a year; the current year is filled in.
- Read whether it is a leap year and why.
- Check the previous and next leap years.
- Enter a start and end year to list all leap years in between.
The leap year rule
The Gregorian calendar, used in the US and most of the world, has three rules:
- A year divisible by 4 is a leap year…
- …unless it is also divisible by 100, then it is not…
- …unless it is also divisible by 400, then it is a leap year after all.
So 2024 and 2028 are leap years, 1900 and 2100 are not, and 2000 was. The calculator tells you which of the three rules applies to the year you enter, and how many days the year and February have.
Why we have leap years
A calendar year of 365 days is a little shorter than the time it takes Earth to go through its seasons, which is about 365.2422 days. Without a correction, the calendar would drift by almost a day every four years, and in a few centuries the spring equinox would land in summer.
Adding February 29 every fourth year gives an average of 365.25 days, which slightly overcorrects. Skipping three of those extra days every 400 years (the century rule) brings the average to 365.2425 days, close enough that the calendar drifts only about one day in roughly 3,000 years. That makes 97 leap years in every 400-year cycle.
Leap years from 2000 to 2100
| Decade | Leap years |
|---|---|
| 2000s | 2000, 2004, 2008 |
| 2010s | 2012, 2016 |
| 2020s | 2020, 2024, 2028 |
| 2030s | 2032, 2036 |
| 2040s | 2040, 2044, 2048 |
| 2050s | 2052, 2056 |
| 2060s | 2060, 2064, 2068 |
| 2070s | 2072, 2076 |
| 2080s | 2080, 2084, 2088 |
| 2090s | 2092, 2096 |
2100 is not a leap year, so 2096 is followed by 2104. For any other range, use the range section of the calculator; it lists up to 4,000 years at a time with the total number of days.
Practical uses
- Age and anniversaries: people born on February 29 (leaplings) usually celebrate on February 28 or March 1 in common years. The age calculator handles this for you.
- Interest and payroll: some calculations use the actual number of days in a year, 365 or 366, so the year type changes the result slightly.
- Day counts: the range summary gives the exact number of days between the start of the first year and the end of the last, which is handy for long-term planning or checking spreadsheet formulas.
- Programming: the rule above is the standard test,
(y % 4 == 0 && y % 100 != 0) || y % 400 == 0.
Years before 1582
The Gregorian calendar was introduced in 1582. Before that, Europe used the Julian calendar, in which every year divisible by 4 was a leap year, with no century exception. The calculator applies today's rule backward (the proleptic Gregorian calendar) and shows a note for those years. Britain and its American colonies switched only in 1752, when September 2 was followed directly by September 14.
Frequently asked questions
Is 2026 a leap year?
No. 2026 is not divisible by 4, so it has 365 days. The next leap year is 2028.
Is 2100 a leap year?
No. 2100 is divisible by 100 but not by 400, so it is a common year with 365 days.
How many leap years are in 400 years?
- There would be 100 if every fourth year counted, but three century years (such as 2100, 2200 and 2300) are skipped.
How often does February 29 happen?
Usually every four years, except in century years not divisible by 400. The gap can therefore be eight years, as between 2096 and 2104.
How many days are in a leap year?
- The extra day is February 29.
Last updated: November 12, 2026