Leap Year Calculator

1. Enter a whole year, such as 2024.
2. Read whether it is a leap year.
3. See the days in the year and in February.
4. The method line lists the next leap years.

Here is what each result means:

A leap year is a year with an extra day, 29 February, making 366 days instead of the usual 365. Leap years exist to keep the calendar in step with the Earth's orbit around the Sun, which takes about 365.2422 days. Without the occasional extra day, the calendar would slowly drift against the seasons.

Adding one day every four years is close, but slightly too much, so the Gregorian calendar refines the rule. A year is a leap year if it is divisible by 4, except for century years, which are leap years only if they are also divisible by 400. That is why 2000 was a leap year but 1900 and 2100 are not.

This three-part rule keeps the calendar accurate to within about one day every 3,000 years. The single skipped leap day at most century boundaries removes the small excess left by the every-four-years rule, which is a neat and durable fix that has kept our dates aligned with the seasons since 1582.

It applies the three-part Gregorian rule to the year you enter.

1. If the year divides by 400, it is a leap year.
2. Otherwise, if it divides by 100, it is not a leap year.
3. Otherwise, if it divides by 4, it is a leap year; if not, it is a common year.

For related tools, see the day of the week calculator and the age calculator.

Check the year 2000.

Result: 2000 divides by 400, so it is a leap year with 366 days and a 29-day February. The year 1900 divides by 100 but not 400, so it is not a leap year, even though it divides by 4. The next leap years after 2000 are 2004, 2008 and 2012.

Each part of the rule handles a different case.

The century exception is the part people forget. Three out of every four century years, such as 1700, 1800 and 1900, are not leap years, while 2000 was. This is what makes the Gregorian calendar more accurate than the older every-fourth-year system.

The leap rule changed when the Gregorian calendar replaced the Julian one.

The Julian calendar added too many leap days, so by 1582 it had drifted about ten days from the seasons. The Gregorian reform dropped three leap days every 400 years to fix this, and its rule is the one this calculator uses for every year.

Divisibility by 4

The starting rule: most years divisible by 4 are leap years, adding a day every four years.

The Century Exception

Years divisible by 100 skip the leap day, correcting the small excess of the four-year rule.

The 400-year Rule

Years divisible by 400 keep their leap day, fine-tuning the calendar to match the solar year.

Planning and Scheduling

Check whether a year has 366 days when counting forward.

Birthdays on 29 February

See which future years actually have a 29 February.

History and Trivia

Settle whether a past century year was a leap year.

1. Forgetting the Century Rule

Not every year divisible by 4 is a leap year. Century years need to divide by 400 too.

2. Assuming 1900 Was a Leap Year

1900 divides by 4 and 100 but not 400, so it was a common year of 365 days.

3. Confusing Julian and Gregorian

Before 1582 the every-fourth-year Julian rule applied, so old dates can differ.

4. Thinking Leap Years Are Exactly Every 4 Years

They usually are, but the skipped century leap days break the simple pattern.

5. Entering a Fraction

A leap year is a whole year. Enter 2024, not 2024.5.

The result follows the Gregorian rule exactly for any whole year you enter.

A leap year has 366 days, with an extra day on 29 February. It keeps the calendar in step with the Earth's orbit, which takes about 365.24 days.

It is a leap year if it divides by 4, except century years, which must also divide by 400. So 2024 and 2000 are leap years, but 1900 and 2100 are not.

Both divide by 4 and 100, but only 2000 divides by 400. The rule keeps 2000 as a leap year while dropping the leap day in 1900.

Yes. 2024 divides by 4 and is not a century year, so it is a leap year with 366 days and a 29-day February.

Leap years usually come every four years, such as 2024, 2028 and 2032. Enter any year and the calculator lists the next few leap years.

A year is about 365.24 days, not exactly 365. Adding a day roughly every four years stops the calendar drifting against the seasons over time.

366 days, one more than a common year of 365. The extra day is 29 February.

Yes. Years divisible by 100 are leap years only if they also divide by 400. This removes the small excess left by the every-four-years rule.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Leap year (Wikipedia).
• Gregorian calendar (Wikipedia).
• Tropical year (Wikipedia).