Leap Year Checker
Check whether any year is a leap year, with a full step-by-step explanation of the Gregorian calendar rules and logic.
How to Use This Calculator
- Enter a year between 1 and 9999 in the input field.
- Click "Check Leap Year" to analyze the year.
- Review the result, rule-by-rule breakdown, and step-by-step explanation.
- See the previous and next leap years for reference.
Formula
1. The year must be divisible by 4.
2. If divisible by 100, it is not a leap year.
3. Unless also divisible by 400, in which case it is a leap year.
Quick Reference: 2000 → Leap (div by 400), 1900 → Not leap (div by 100 but not 400), 2024 → Leap (div by 4 not 100), 2025 → Not leap.
Examples
Divisible by 4 ✓, by 100 ✓, by 400 ✓ → Leap year (366 days).
Divisible by 4 ✓, by 100 ✓, by 400 ✗ → Not a leap year (365 days).
Divisible by 4 ✓, by 100 ✗ → Leap year (366 days). February has 29 days.
Frequently Asked Questions
Why do we have leap years?
A leap year adds an extra day to keep our calendar aligned with the Earth’s orbit around the Sun. The Earth orbits in approximately 365.2422 days, so without leap years, the calendar would drift about 1 day every 4 years.
What happens if you are born on February 29?
Leaplings typically celebrate their birthday on February 28 or March 1 in non-leap years. Legally, most countries recognize March 1 as the official birthday for non-leap year purposes.
Do all calendars have leap years?
Many calendars (Gregorian, Chinese, Hebrew, Islamic) have some form of intercalation, but the rules vary significantly. The Gregorian calendar’s leap year system is the most widely used globally.
What is the next leap year?
Leap years occur every 4 years (with century exceptions). The next leap years are 2028, 2032, 2036, 2040, and so on.