Leap Year Checker
Check whether a year is a leap year under the Gregorian rule and find the previous and next leap years.
Your inputs
Results
Leap year?
Yes
- Because it is
- divisible by 4 and not by 100
- Days in the year
- 366
- Next leap year
- 2,028
- Previous leap year
- 2,020
✓Exact calculation — rounded only for display
Notes for this result
- Gregorian rule. Years before the calendar’s adoption (1582 and later, depending on country) are treated proleptically.
What this calculator does
Leap years add 29 February to keep the calendar aligned with the solar year.
Formula and method
Leap if divisible by 4, except years divisible by 100 unless also divisible by 400.
Worked example
Calculated by this tool with its default inputs:
Inputs
- Year: 2024
Results
- Leap year?: Yes
- Because it is: divisible by 4 and not by 100
- Days in the year: 366
- Next leap year: 2,028
- Previous leap year: 2,020
How to read the results
1900 was not a leap year; 2000 was.
Assumptions and limitations
- Applies the Gregorian rule to all years.
Questions
How long is the average Gregorian year?
365.2425 days.
Methodology and verification
- Result type
- Exact mathematical calculation (rounded only for display)
- Formula version
- 1.0
- Automated verification
- 4 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
- Editorial review
- Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.
Privacy
Everything you enter is calculated in this browser and is not sent to Numerith or anyone else. Inputs are added to a share link only if you choose to include them. Privacy policy