Leap Year Checker & Calendar Formula Explainer
Because Earth takes approximately 365.2422 days to orbit the Sun, calendar systems add an extra leap day (February 29) periodically. Verify any year instantly with mathematical breakdown.
How to Use Leap Year Checker
Enter Year
Type any four-digit or astronomical year (e.g., 2024, 2028, or 2100).
Review Verdict
See an instant YES or NO result with 365 vs 366 total days.
Inspect Formula Rules
Review whether the year passed or failed the divisible by 4, 100, and 400 criteria.
About Leap Year Checker
A year is a leap year if (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0). For example, 2000 was a leap year, but 1900 was not, and 2100 will not be.
Supported Formats
Operational Limits
- •Uses Gregorian calendar rules established in 1582; pre-1582 dates are proleptic.
Key Features
- Instant evaluation of any year from 1 to 99,999
- Full 3-step Gregorian algorithm breakdown (divisible by 4, not 100, unless 400)
- List of upcoming next 10 leap years
- Calculates exact number of days (365 vs 366) and total hours
- Astronomical solar year drift explanation
Frequently Asked Questions
Related Tools
More in Date & Time UtilitiesDate Addition & Subtraction Calculator
Add or subtract exact years, months, weeks, days, hours, and minutes to or from any calendar date with business day calculations.
Week Number Calculator
Look up the ISO 8601 week number, start and end dates, day of year, and remaining weeks for any calendar date.
Day of the Week Calculator
Find the exact day of the week (Monday through Sunday) for any historical or future calendar date with Conway's Doomsday rule.