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Days in the year
Check instantly whether any year is a leap year, and why.
Enter any year and this tool instantly tells you whether it's a leap year, explains exactly which divisibility rule made the difference, shows how many days that year contains, and finds the next leap year after it. It's a quick, no-ambiguity answer to a rule that a surprising number of people misremember.
Most people learn the simple version: a leap year is any year divisible by 4. That's true most of the time, but there's a widely-forgotten exception — a year divisible by 100 is not a leap year, unless it's also divisible by 400. That's why 2000 was a leap year (divisible by 400) but 1900 was not (divisible by 100 but not 400), even though both are divisible by 4. This calculator applies the full three-part rule every time, not just the simplified version, so it's correct for century years as well as ordinary ones.
A solar year — the actual time it takes Earth to orbit the sun — is approximately 365.2422 days, not a clean 365. Without correction, using a fixed 365-day calendar would drift out of sync with the seasons by about a day every four years, and by roughly 25 days per century. Adding a leap day roughly every four years keeps the calendar closely aligned with the solar year, and the extra century-year exception fine-tunes that alignment even further over long timescales.
Software developers need to handle leap years correctly in any date-related code, since off-by-one bugs around February 29th are a classic source of calendar bugs. Financial and payroll systems that calculate daily rates need to know whether a given year has 365 or 366 days. And plenty of people simply want to know if a specific year matters for a February 29th birthday they're tracking, since 'leaplings' only get a true birthday once every four years in most cases.
Because the century-year exception makes leap years slightly irregular, it isn't always obvious how many years until the next one without checking each candidate year in turn. This tool automatically steps forward from your entered year and applies the full rule to each candidate until it finds the next genuine leap year, so you don't have to work through the divisibility checks by hand.
Almost, but not quite — years divisible by 100 are the exception and are NOT leap years, unless they're also divisible by 400. So 2100, 2200 and 2300 will not be leap years, but 2000 and 2400 are.
Yes. Even though 2000 is divisible by 100, it's also divisible by 400, which makes it a leap year under the full rule.
366 days, with the extra day added as February 29th.
Roughly every 4 years, except for century years not divisible by 400, which are skipped.
Most systems and individuals informally treat February 28th (or sometimes March 1st) as the observed birthday in non-leap years, though this calculator only reports the leap year status itself, not a substitute birthday convention.