Leap Year Checker
Determine whether a year is a Gregorian leap year and show whether it contains 365 or 366 days.
How to use
- Select any date in the year you want to check.
- Calculate.
- Read leap/common year and total days.
Capabilities and scope
The checker applies the familiar divisible-by-4, century, and divisible-by-400 rules that determine whether February 29 exists.
How it works
A year is leap when divisible by 4, except century years divisible by 100 are common unless they are also divisible by 400.
Example
2000 is a leap year because it is divisible by 400; 1900 is a common year because it is a century not divisible by 400.
Useful for
- Validate February dates
- Confirm annual day counts
- Prepare date-algorithm test cases
Before you use it
- The modern Gregorian rule is applied proleptically and does not model the historical adoption date of the calendar in each region.
Standards and references
Frequently asked questions
Is every year divisible by 4 a leap year?
No. Century years are common unless also divisible by 400.
How many days are in a leap year?
366, because February 29 is added.