Leap Year Calculator

Check whether any given year is a leap year in the Gregorian calendar.

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Check whether any given year is a leap year in the Gregorian calendar.

How It Works

How Leap Year Calculator Works

A year is a leap year if it divides evenly by 4 — unless it also divides evenly by 100, in which case it isn't a leap year after all, unless it divides evenly by 400, in which case it is one again. That extra layer of exceptions is what keeps the calendar accurately synced with Earth's actual orbit over long stretches of time.

Worked Example

See It In Action

The year 1900 divides evenly by 4 and by 100 but not by 400, so it was not a leap year — while 2000 divides evenly by 400 too, so it was one.

Real-World Use Cases

Who Uses Leap Year Calculator and Why

Checking whether a specific birth year, historical year, or planning year is a leap year before relying on a February 29th date.
Verifying leap year status when building or checking a calendar, schedule, or date-related script.
Settling a quick factual question about a specific century year, like 1900 or 2000, where the leap year rule gets less intuitive.
Confirming a leap year assumption before scheduling a February 29th-dependent event or anniversary.

Common Mistakes

Mistakes to Avoid

Assuming every year divisible by 4 is automatically a leap year — century years (divisible by 100) are the exception, unless they're also divisible by 400.
Forgetting the double exception — a year like 2000, divisible by both 100 and 400, is a leap year after all, which trips people up more than any other case.

Pro Tips

Tips for Best Results

For century years specifically (ending in 00), check divisibility by 400 rather than assuming the standard divide-by-4 rule applies.
Use this before planning any recurring February 29th event to confirm which years it actually falls in.

Troubleshooting

Fixing Common Problems

I expected a century year to be a leap year and it wasn't. — Century years follow a special exception — they're only leap years if divisible by 400, not just by 4 or 100; 1900 is a classic example of a non-leap century year.

Glossary

Terms Explained

Leap year rule: A year is a leap year if divisible by 4, except century years, which must be divisible by 400 to qualify.

FAQ

Frequently Asked Questions

Why does the calendar need leap years at all?

Earth's orbit around the sun takes about 365.2422 days, not an even 365 — adding an extra day roughly every 4 years keeps the calendar from slowly drifting out of sync with the actual seasons.

Why the extra exception for century years?

A leap year every 4 years alone slightly overcorrects, since 365.25 is a bit more than the true value — skipping the leap day in three out of every four century years (like 1900, but not 2000) fine-tunes the average length much closer to the real solar year.