Date & Time
Leap Year Calculator
Leap Year: leap Year Calculator applies the Gregorian rule — a year is a leap year if divisible by 4, except centuries, which must be divisible by 400 — so the year has 366 days (February 29) or 365. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
Use Leap Year Calculator to check whether a year is a leap year: give it your year, press Calculate, and read off a leap-year verdict and the year length — all worked out on your device.
About this calculator
It matters whenever spans between dates, times or zones drive a plan, a deadline or a record. The governing relationship: Leap Year Calculator applies the Gregorian rule — a year is a leap year if divisible by 4, except centuries, which must be divisible by 400 — so the year has 366 days (February 29) or 365. See it on real numbers: 2024 is a leap year (divisible by 4 and not a non-400 century), so February has 29 days ; 1900 was not a leap year. The calculator above applies the same steps to whatever you enter — computed locally, nothing sent anywhere.
How to use
- Enter the year you want to check.
- Press Calculate to test the year.
- See whether the year is a leap year.
- Check the number of days in February and in the whole year.
Why use Leap Year Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard calendar arithmetic where applicable. Check critical schedules, payroll, and official holiday dates before relying on results.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it when validating a date in code
Use it for spotting leap years in a range
Use it when a 366-day year matters
Use it for everyday calendar reference
Use it when explaining the 100/400 rule
Use it when teaching the leap-year rule
Technical notes
Leap Year Calculator applies the Gregorian rule — a year is a leap year if divisible by 4, except centuries, which must be divisible by 400 — so the year has 366 days (February 29) or 365.
Calculations use the calendar only and do not adjust for time-zone shifts unless a field asks for a zone.
All arithmetic runs in your browser using double-precision floating point, so extreme inputs may show tiny rounding differences.
FAQ
What makes a year a leap year?
A year is leap if it is divisible by 4, except century years, which must also be divisible by 400 — so 1900 is not a leap year but 2000 is.
How many days does the year have?
A leap year has 366 days with 29 days in February; a common year has 365 days with 28 days in February.
Does it work for any year?
Enter any whole year and it applies the Gregorian leap-year rule to tell you whether the year is leap.
Does the Leap Year Calculator send my data to a server?
No. The Leap Year Calculator runs entirely in your browser — your inputs never leave your device, and nothing is uploaded or stored.
Worked example
2024 is a leap year (divisible by 4 and not a non-400 century), so February has 29 days; 1900 was not a leap year.