How to use the leap year checker
- Type a Year between 1 and 9999.
- The answer appears at once: “Yes, a leap year” or “No, a common year”.
- Under it you get the days in the year, the days in February, and the previous and next leap years.
- The Why box names the rule that applied, and Leap years from here lists the next ten, starting with your year if it is one.
What it does and when to use it
Leap years matter more often than people expect. They change the length of February in payroll and rent schedules. They decide whether a 29 February birthday happens this year, and they make 52-week plans drift by a day. Programmers check them when testing date code, and teachers use them for divisibility lessons.
To see the full month-by-month calendar for a year, use the days in month calculator. If you were born on 29 February, the age calculator shows how it counts your birthday in other years. To count days across a leap day, use the date difference calculator.
How it works
The Gregorian calendar has three rules, checked in this order:
| Test | Result | Example |
|---|---|---|
| Divisible by 400 | Leap year | 2000, 2400 |
| Divisible by 100 (but not 400) | Common year | 1900, 2100 |
| Divisible by 4 (but not 100) | Leap year | 2024, 2028 |
| Anything else | Common year | 2026, 2027 |
So 97 of every 400 years are leap years, giving an average year of 365.2425 days. The previous and next leap years come from stepping one year at a time until the rule says yes, which handles century gaps correctly.
Worked examples
2100. The checker answers “No, a common year” and explains: 2100 is divisible by 100 but not by 400, so it is not a leap year. The previous leap year is 2096 and the next is 2104.
2028. Yes, a leap year with 366 days and 29 days in February. Previous leap year: 2024, next 2032.
1500. The Gregorian rule says common year (divisible by 100, not by 400). The tool adds the note Before 1582 this uses the Gregorian rules extended backwards (proleptic), because 1500 was a leap year in the Julian calendar used then.
Limits and tips
- Years must be whole numbers from 1 to 9999. Year 0 and BC years are not supported.
- Countries switched to the Gregorian calendar in different years (Britain and its colonies in 1752, for example), so check historical dates against local records.
Frequently asked questions
Is 2000 a leap year?
When is the next century year that is not a leap year?
Why do we need leap years at all?
Why does the tool add a note for old years?
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