Week, Month & Year Tools
Educational
Leap Year Checker
Check if any year is a leap year and explore the 4/100/400 Gregorian calendar rule.
Leap Year Status
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366 Days (February has 29 days)
Yes
Divisible by 4?
No
Century Year (/100)?
N/A
Divisible by 400?
Previous Leap Year: 2024
Next Leap Year: 2028
About the Leap Year Checker
Is a given year a leap year? The Leap Year Checker tests any year in history or the future against the three-part astronomical Gregorian rule, explaining exactly why years like 2000 were leap years while years like 1900 and 2100 are common years.
How to Use This Calculator
- Enter any Year (e.g., 2024, 2026, 2028, 2100).
- Click Check Year.
- Review the step-by-step mathematical logic and upcoming leap years.
Calculation Method & Mathematical Formula
The Gregorian leap year algorithm tests three hierarchical conditions:
- If
Year % 400 == 0→ Leap Year (e.g. 2000, 2400). - Else if
Year % 100 == 0→ Common Year (e.g. 1800, 1900, 2100). - Else if
Year % 4 == 0→ Leap Year (e.g. 2024, 2028). - Otherwise → Common Year (e.g. 2025, 2026, 2027).
Worked Example
Scenario: Checking 2028 and 2100:
- 2028: Divisible by 4, not by 100 → Leap Year (366 days).
- 2100: Divisible by 4 and by 100, but NOT by 400 → Common Year (365 days).
Important Calendar Notes
This correction aligns the calendar year with the Earth’s tropical orbital year (approx. 365.2422 solar days).
Frequently Asked Questions
Related Calculators
Last reviewed by editorial team on September 13, 2026
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Disclaimer: The Gregorian reform was introduced in 1582; prior dates followed the Julian calendar system.