Leap Year Checker
Check whether a year is a leap year and why.
What is Leap Year?
A tiny but exact calendar tool. It applies the full Gregorian leap-year rule — 2000 was a leap year, 1900 was not.
How it works
The rule is: divisible by 4, but not by 100, unless also divisible by 400. The tool also reports February's length for that year.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
The century rule
2024 is a leap year and 2000 is too, but 1900 is not — divisible by 4 but also by 100, and not by 400. The checker explains exactly why.
Common mistakes
Every fourth year isn't enough
The full rule is: divisible by 4, except century years, which must also be divisible by 400. 1900 and 2100 are the traps.
Frequently asked questions
Why does the rule exist?
It keeps the calendar aligned with the solar year — one leap day every four years overcorrects slightly, so century years skip unless divisible by 400.
Can I check a range of years at once?
Yes — enter a range and get every leap year in it, handy for date-validation and payroll logic.
Is February 29 valid in a non-leap year?
No — the checker flags Feb 29 in non-leap years as invalid, which is a common input-validation bug in software.