A leap year adds a 366th day, February 29, to keep the calendar in step with the seasons. This calculator tells you whether any year is a leap year and walks through the divisibility test, or lists every leap year between two years along with the weekday its leap day falls on.
How to use the leap year calculator
- Choose Check a year or List leap years.
- To check, enter the year. The tape answers yes or no, shows the number of days, the weekday of February 29 if it exists, and the previous and next leap years.
- To list, enter a from and to year (up to 4,000 years apart). The table shows each leap year with the weekdays of February 29 and January 1.
The leap year rule
The Gregorian calendar, used for civil dates in the United States and almost everywhere else, defines a leap year with three tests applied in order:
- If the year is not divisible by 4, it is a common year (365 days).
- If it is divisible by 4 but not by 100, it is a leap year (366 days).
- If it is divisible by 100, it is a leap year only if it is also divisible by 400.
That gives 97 leap years every 400 years and an average year of 365 + 97/400 = 365.2425 days, within about 27 seconds of the mean tropical year.
Worked examples
2028: 2028 ÷ 4 = 507, a whole number; 2028 ÷ 100 = 20.28, not whole. Leap year.
2100: divisible by 4 (525) and by 100 (21), but 2100 ÷ 400 = 5.25. Common year. February 2100 will have 28 days.
2000: divisible by 4, by 100 and by 400 (exactly 5). Leap year. That made 2000 the first century leap year since 1600.
2026: 2026 ÷ 4 = 506.5. Common year.
Upcoming leap years
| Leap year | February 29 falls on |
|---|---|
| 2028 | Tuesday |
| 2032 | Sunday |
| 2036 | Friday |
| 2040 | Wednesday |
| 2044 | Monday |
| 2048 | Saturday |
Because each four-year cycle contains 1,461 days, which is 208 weeks plus 5 days, February 29 moves five weekdays later (or two earlier) each time it comes around, as the table shows.
A short history of leap days
Julius Caesar’s calendar reform of 46 BC introduced a leap day every fourth year, an average year of 365.25 days. That is about 11 minutes too long, and by the 1500s the spring equinox had drifted roughly 10 days earlier on the calendar. In 1582 Pope Gregory XIII dropped 10 days and introduced the century exception used today. Britain and its American colonies did not switch until 1752, when Wednesday, September 2 was followed directly by Thursday, September 14.
The calculator applies the Gregorian rule to every year, including those before 1582 (the proleptic Gregorian calendar). Under the old Julian rule, years such as 1500 and 1700 were leap years.
Leap years in everyday calculations
- Ages and anniversaries: someone born on February 29 has a true birthday only in leap years; the age calculator and birthday calculator let you choose February 28 or March 1 for common years.
- Day counts: a span that crosses February 29 is one day longer than the same span a year earlier. The date difference calculator counts it automatically.
- Weekdays: a date moves two weekdays after a leap day instead of one, which you can check with the day of the week calculator.
Frequently asked questions
Is 2028 a leap year?
Yes. 2028 is divisible by 4 and not by 100, so it has 366 days and a February 29, which falls on a Tuesday. The previous leap year was 2024 and the next after 2028 is 2032.
Why was 2000 a leap year but 1900 was not?
Century years are leap years only when divisible by 400. 2000 ÷ 400 = 5 exactly, so 2000 was a leap year; 1900 ÷ 400 = 4.75, so 1900 was a common year. The next century year that skips its leap day is 2100.
How many leap years are there between 2000 and 2100?
There are 25: every fourth year from 2000 through 2096. The year 2100 is divisible by 100 but not 400, so it is not a leap year.
Why do we need leap years at all?
Earth takes about 365.2422 days to go through its seasons once. Without an extra day roughly every four years, the calendar would drift against the seasons by almost a day every four years and about 24 days per century.