Free tool · Time
Leap Year Checker
Check whether a given year is a leap year, and find the next one.
Enter any year to instantly check whether it is a leap year (366 days, with February 29th) according to the standard Gregorian calendar rule, and see when the next leap year will occur.
- Nothing leaves your device
- Runs entirely in your browser
- Free, no account needed
How to use Leap Year Checker
Two steps, and nothing to install.
Enter a year
Any whole number year works, historical or far in the future.
Read the result
You get a straight answer plus the next leap year.
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Open ToolHow this works in your browser
The check applies the Gregorian rule in full: divisible by four is a leap year, unless divisible by one hundred, unless also divisible by four hundred. Those three nested conditions exist because each corrects an overcorrection in the one before it, producing an average year of 365.2425 days against the true orbital period of roughly 365.2422. Implementing all three rather than the commonly shortened divisible-by-four version matters precisely because the shortcut gives correct answers for every year from 1901 to 2099, which is why so much software carries the bug undetected. Everything is computed in your browser.
Leap Year Checker vs. typical online calculators
| Feature | Leap Year Checker (in-browser) | Typical online calculators |
|---|---|---|
| Where the maths runs | In your browser, on your device | Often posted to a server to compute |
| Your inputs are stored | Never - nothing is sent or saved | Frequently logged with your session |
| Works offline once loaded | Yes | No - needs a live connection |
| Ads inside the result area | None | Common on free calculators |
| Account required | No | Often, to save or export results |
| Usage limits | None - free, unlimited use | Sometimes capped per day |
Who uses Leap Year Checker
Checking a specific year
Confirm whether a past or future year has 29 February.
Planning around February dates
Work out when a date near the end of February falls.
Teaching the calendar rule
Demonstrate why 1900 and 2000 differ despite both being century years.
Verifying date logic
Check expected results when testing software that handles dates.
Frequently asked questions
What it can and cannot do, and what happens to your files.
What is the leap year rule?
A year is a leap year if it is divisible by 4, except for century years (divisible by 100), which must also be divisible by 400 - this is why 2000 was a leap year but 1900 was not.
Why do leap years exist?
They keep the calendar year synchronized with Earth’s orbit around the sun, which takes approximately 365.24 days, not exactly 365.
Can I check years far in the future or past?
Yes, the calculation works for any whole number year, positive or historical.
Why was 1900 not a leap year when 2000 was?
Because of the century rule. Adding a day every four years slightly overcorrects, so century years are skipped to compensate, and every fourth century is reinstated because that skip slightly overcorrects in turn. 1900 was divisible by 100 but not 400, so it was skipped; 2000 was divisible by 400, so it was not.
Why do so many systems get this wrong?
Because 2000 was a leap year under the exception to the exception, so software that implemented only the simple divisible-by-four rule behaved correctly through the entire period most systems were tested in. The next century year, 2100, is where that shortcut finally breaks.
How accurate is the Gregorian rule?
Remarkably. The three nested rules give an average year of 365.2425 days against an actual orbit of about 365.2422, which drifts by roughly one day every three thousand years. That precision is why the calendar has needed no adjustment since its introduction.
What happens to people born on 29 February?
Legally it varies by jurisdiction, with some treating 28 February as the birthday in common years and others 1 March. Socially most people simply pick one. The actual date recurs only every four years, or eight when a skipped century intervenes.
Check if a year is a leap year - free.
Files never leave your device. No upload, no account, and free for unlimited use.