Leap Year Checker
Check whether a year is a leap year.
Check whether a year is a leap year.
Year check
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Tool guide
Free Online Leap Year Checker
Check an integer year with the modern Gregorian leap-year rule and see a concise explanation of the result. The browser-first test distinguishes ordinary fourth years from century exceptions.
Steps
How it works
- Enter an integer year.
- Run the leap-year check.
- Review whether the year passes the Gregorian rule.
- Copy or download the explanation.
Highlights
Key features
- Applies divisibility by 4, 100, and 400.
- Explains the century-year exception in the result.
- Accepts one integer year at a time.
- Rejects non-integer and non-numeric input.
- Works locally in the browser.
Use cases
Common uses
- Check whether February has 29 days in a Gregorian year.
- Explain why 2000 was a leap year but 1900 was not.
- Test a year while validating calendar logic.
- Learn the modern Gregorian leap-year rule.
Notes
Limitations to know
- The tool applies the proleptic Gregorian arithmetic rule to any accepted integer.
- It does not model regional adoption dates or other historical calendars.
- Julian-calendar leap-year rules are not supported.
- There is no configured year range, and year zero or negative integers are tested mathematically rather than historically.
- The checker handles one year at a time and does not suggest nearby leap years.
FAQ
Frequently asked questions
What is the Gregorian leap-year rule?
A year is a leap year when divisible by 4, except century years must also be divisible by 400.
Why was 2000 a leap year but 1900 was not?
Both are century years, but 2000 is divisible by 400 while 1900 is not.
Is every fourth year a leap year?
Usually, but years divisible by 100 are exceptions unless they are also divisible by 400.
Does the tool use the Gregorian calendar?
Yes. It applies the modern Gregorian divisibility rule.
Can it accurately check historical years before Gregorian adoption?
It can apply the arithmetic rule, but it does not model which calendar a region actually used at that time.