A solar year is about 365.2422 days, so the Gregorian calendar adds a 29 February in 97 of every 400 years: every fourth year, except century years not divisible by 400. 2000 was a leap year; 1900 and 2100 are not.
How to use the Leap Year Calculator
- Year
- Count from year
- Count to year
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter a year, and optionally a range of years to count leap years in.
Upcoming leap years
2028, 2032, 2036, 2040, 2044, 2048, 2052, 2056, 2060, 2064, 2068, 2072, 2076, 2080, 2084, 2088, 2092, 2096 – then 2104 (2100 is skipped).
Tips
- Check whether the end date should be included – event durations usually include it, elapsed time does not.
- Months have 28–31 days, so “one month” is counted by calendar date, not as 30 days.
- Use 24-hour time or set AM/PM carefully when entering clock times.
- Time zones and daylight-saving changes are not applied unless the calculator says so.
Common mistakes to avoid
- Counting a 30-day month when a calendar month is meant (or the reverse).
- Forgetting leap years when counting days across February.
- Mixing decimal hours (7.5 h) with clock time (7:30).
Inputs explained
| Field | What to enter |
|---|---|
| Year | A number |
| Count from year | A number |
| Count to year | A number |
Formula
Leap year if divisible by 4, except century years, which must be divisible by 400Leap years up to y: L(y) = ⌊y/4⌋ − ⌊y/100⌋ + ⌊y/400⌋Worked example
Inputs — Year: 2,026; Count from year: 2,000; Count to year: 2,100.
Results — Is it a leap year? = No – 365 days; Next leap year = 2028; Previous leap year = 2024; 29 February falls on a = Tuesday; Leap years in the range = 25.
Frequently asked questions
Is 2028 a leap year?
Yes – it is divisible by 4 and not a century year.
Why isn't 2100 a leap year?
Century years are leap years only when divisible by 400.
How often is there a leap year?
Usually every 4 years, 97 times every 400 years.
What formula does the Leap Year Calculator use?
Leap year if divisible by 4, except century years, which must be divisible by 400.