What makes a year a leap year?

A year is a leap year if it is divisible by 4, except for century years, which must also be divisible by 400. So 2000 was a leap year but 1900 was not. This checker applies that rule and explains which part of it decided the result.

Why do century years like 1900 break the simple rule?

The extra divisible-by-100-but-not-400 exception keeps the calendar aligned with the solar year. Without it, the calendar would drift by about three days every 400 years.

Is anything sent to a server?

No. The check is pure local arithmetic in your browser — no data is uploaded or stored.

Yes. 2024 is divisible by 4 and is not a century year, so it is a leap year with 366 days, including 29 February.

No. 2100 is divisible by 4 and by 100, but not by 400, so the century exception makes it a common year of 365 days.

When is the next leap year?

Leap years fall every four years in most cases: 2024, 2028, 2032 and so on. Enter any year and the checker also tells you the next leap year after it.

How many days are in a leap year?

A leap year has 366 days — one extra day, 29 February, added to the usual 365. This keeps the calendar synchronised with Earth's orbit, which takes about 365.2422 days.

Why is there a leap year at all?

Earth takes roughly 365.2422 days to orbit the Sun. Adding one day every four years (with the century corrections) keeps the calendar from drifting out of step with the seasons.

Leap Year Checker — Gera Tools

A leap year has 366 days instead of 365, adding 29 February to keep the calendar synchronised with Earth’s orbit. This checker tells you instantly whether any year — past or future — is a leap year or a common year, explains exactly which rule decided it, and shows the next leap year. It is handy for scheduling, date arithmetic, history questions and anyone born on 29 February.

How it works

The tool applies the Gregorian leap-year rule, which is a single boolean expression:

A year is a leap year if it is divisible by 4 AND not divisible by 100 — OR if it is divisible by 400.

In order of precedence the checker tests:

Divisible by 400 → leap year (e.g. 2000)
Otherwise divisible by 100 → common year (e.g. 1900, 2100)
Otherwise divisible by 4 → leap year (e.g. 2024)
Otherwise → common year (e.g. 2023)

The century corrections matter because Earth’s orbit is about 365.2422 days, not a clean 365.25. Adding a day every 4 years overcorrects slightly, so three leap days are removed every 400 years.

Example

Year	Divisible by 4?	Divisible by 100?	Divisible by 400?	Result
2024	Yes	No	—	Leap (366 days)
2023	No	—	—	Common (365 days)
1900	Yes	Yes	No	Common (365 days)
2000	Yes	Yes	Yes	Leap (366 days)

For 2024: it is divisible by 4 and not by 100, so it is a leap year; the next leap year is 2028.

The check is pure local arithmetic in your browser — nothing is uploaded or stored.