How to use the leap year calculator
- Enter a year from 1 to 9999.
- Read whether it is a leap year, with the reason in plain words, and how many days the year and February have.
- See the previous and next leap years, and the weekday that February 29 falls on when the year has one.
- Open the advanced options to change how many upcoming leap years the table lists, up to 40. Export the table as CSV if you need it.
Formula
leap year if the year is divisible by 4
except if it is divisible by 100
unless it is also divisible by 400
So 2028 and 2032 are leap years, 1900 and 2100 are not, and 2000 and 2400 are. A leap year has 366 days because February has 29.
Three years compared
2028 is divisible by 4 and not by 100, so it is a leap year with 366 days, and February 29, 2028 is a Tuesday. 1900 is divisible by 100 but not by 400, so it is not a leap year and has 365 days. 2000 is divisible by 400, so it is a leap year even though it is a century year, and February 29, 2000 was a Tuesday.
Starting from 2028 the next leap years are 2032, 2036, 2040, 2044, 2048, 2052 and 2056. February 29 falls on a Tuesday in 2028, a Sunday in 2032 and a Friday in 2036.
Why leap years exist
The Earth takes about 365.2422 days to go around the Sun. A calendar of exactly 365 days would drift out of step with the seasons by almost a day every four years, so an extra day is added to most fourth years. Adding one every fourth year alone would overshoot slightly, which is why century years skip it unless they are divisible by 400.
Averaged over 400 years the rule gives 365.2425 days a year, close enough that the calendar drifts by only about a day in more than 3,000 years.
Things that depend on leap years
Leap years change day counts between dates, ages measured in days and yearly percentages. A birthday on February 29 is celebrated on a different date in common years depending on local custom. The days between dates calculator and the day of the week calculator both account for February 29, and the year progress calculator uses 366 days for the year.
Assumptions and limits
- The Gregorian rule is applied to every year from 1 to 9999, including years before the calendar was adopted in 1582 and the later dates when different countries switched.
- Years in the older Julian calendar, where every fourth year was a leap year, are not modeled.
- The weekday of February 29 is computed on the same proleptic Gregorian calendar.
- Calendars that add whole months, such as some lunisolar calendars, follow different rules and are not covered.
Frequently asked questions
Is 2100 a leap year?
No. 2100 is divisible by 100 but not by 400, so it is a common year with 365 days. The next century leap year after 2000 is 2400.
How often do leap years happen?
Usually every four years, with the exception of century years not divisible by 400. In every 400 year cycle there are 97 leap years, which makes the average year 365.2425 days long.
What is the next leap year?
Enter the current year and read the next leap year line. If the year you enter is itself a leap year, the next one is four years later, except where a century year is skipped.
What weekday is February 29?
It depends on the year, and it moves forward through the week across leap years. The table lists the weekday for each upcoming leap year so you can see the pattern.