About Leap Year Checker
Verify leap years from 1 AD to 9999 AD and understand the astronomical rationale behind the 400-year cycle.
Calculation Methodology & Formula
A year is a leap year if divisible by 4, except end-of-century years (ending in 00), which must also be divisible by 400 (e.g., 2000 was a leap year, but 1900 and 2100 are not).
How to Use This Calculator
- Enter any 4-digit year (e.g. 2024, 2028, 1900).
- Click "Check Leap Year".
- Read the detailed explanation, days in February, and adjacent leap years.
Frequently Asked Questions
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