Leap Year Calculator

A year is a leap year when it divides evenly by 4, with one exception: years that divide by 100 are skipped unless they also divide by 400. That single exception is why the rule looks more complicated than 'every four years'.

Both years divide by 4 and by 100, so the century exception removes them from the normal cycle. Only 2000 also divides by 400, which puts it back in, while 1900 stays a 365 day common year.

A leap year has 366 days because February gains a 29th day. A common year has 365 days, and the tool shows the exact figure for whichever year you enter.

You can enter any whole number, including large future years, and the arithmetic stays exact. Keep in mind the Gregorian calendar was only adopted in 1582, so applying its rule to much older years is a mathematical projection rather than a historical fact.

No. The field expects a whole-number year, and entering a decimal, a blank, or letters shows a short prompt to enter a whole-number year instead of a result.

It steps outward one year at a time from the year you entered and stops at the first leap year it finds in each direction. That means even if you type a leap year itself, the neighbours shown are different years.

Usually, but not always. Around a skipped century such as 1900, the gap stretches to eight years (from 1896 to 1904), which the previous and next figures make visible.

Earth takes about 365.2422 days to orbit the Sun, so a fixed 365 day year drifts against the seasons. Adding a day most four-year cycles, then trimming three of those additions every 400 years, keeps the calendar closely aligned.

Yes. Every calculation runs locally in your browser and no year you type is ever uploaded to a server.