📅 Leap Year Calculator
By ToolNimba Editorial Team · Updated 2026-06-19
This leap year checker tells you in one step whether a given year is a leap year. Type in any year and it shows the verdict, the exact reason behind it, how many days February has that year, the total days in the year, and the next five leap years coming up. It works for past, present, and future years, so you can check 1900, 2000, this year, or a date far ahead.
What is the Leap Year Checker?
A leap year is a year with 366 days instead of the usual 365, with the extra day added as February 29. We need leap years because the Earth takes roughly 365.2422 days to orbit the Sun, not a tidy 365. If the calendar ignored that extra quarter of a day, the seasons would slowly drift out of step with the months, and after a few centuries summer would land in what the calendar calls winter.
The modern Gregorian rule keeps the calendar lined up with three nested tests. First, a year is a leap year if it is divisible by 4. Second, century years (those ending in 00) are an exception and are not leap years, even though they divide by 4. Third, there is an exception to that exception: century years divisible by 400 are leap years after all. So 2024 is a leap year, 1900 is not (divisible by 100 but not 400), and 2000 is (divisible by 400).
This combination is more accurate than the older Julian rule, which simply made every fourth year a leap year. The Julian calendar added too many leap days over time, drifting about three days every 400 years. The Gregorian fix drops three leap days every 400 years by skipping most century years, which keeps the average calendar year at 365.2425 days, very close to the true solar year.
When to use it
- Confirming whether a particular year has a February 29 before scheduling an event or anniversary.
- Checking how many days a year has when building a date calculation, payroll period, or interest accrual.
- Settling a debate about whether century years like 1900 or 2100 are leap years.
- Teaching or learning the divisible by 4, 100, and 400 rule with real worked examples.
How to use the Leap Year Checker
- Type a year into the year box, or use the quick buttons for this year, 2000, 2024, or 2100.
- Read the verdict at the top: it states clearly whether the year is a leap year.
- Check the reason line to see exactly which part of the rule applied.
- Look at the days in February and total days in the year for that specific year.
- Scroll the next leap years list to plan ahead for upcoming February 29 dates.
Formula & method
Worked examples
Is 2024 a leap year?
- 2024 divided by 4 leaves no remainder, so it passes the first test.
- 2024 is not a century year (it does not end in 00), so the exception does not apply.
- The first test passes and no exception applies, so 2024 is a leap year.
Result: 2024 is a leap year with 366 days and a February 29.
Is 1900 a leap year?
- 1900 divided by 4 leaves no remainder, so it passes the first test.
- 1900 is a century year (divisible by 100), so it is normally excluded.
- 1900 divided by 400 leaves a remainder of 300, so the 400 exception does not save it.
- The century exception stands, so 1900 is not a leap year.
Result: 1900 is a common year with 365 days and only 28 days in February.
Is 2000 a leap year?
- 2000 divided by 4 leaves no remainder, so it passes the first test.
- 2000 is a century year (divisible by 100), so it is normally excluded.
- 2000 divided by 400 leaves no remainder, so the 400 exception makes it a leap year.
Result: 2000 is a leap year with 366 days, unlike 1900 and 2100.
How the rule decides recent and notable years
| Year | Divisible by 4 | Century year | Divisible by 400 | Leap year? |
|---|---|---|---|---|
| 2024 | Yes | No | n/a | Yes |
| 2025 | No | No | n/a | No |
| 2026 | No | No | n/a | No |
| 2028 | Yes | No | n/a | Yes |
| 1900 | Yes | Yes | No | No |
| 2000 | Yes | Yes | Yes | Yes |
| 2100 | Yes | Yes | No | No |
| 2400 | Yes | Yes | Yes | Yes |
Common mistakes to avoid
- Assuming every fourth year is a leap year. The divisible by 4 test alone is the old Julian rule. Under the Gregorian calendar we use today, century years like 1900 and 2100 are skipped unless they also divide by 400.
- Thinking all century years are skipped. Century years are usually not leap years, but the ones divisible by 400 are. That is why 2000 was a leap year even though 1900 and 2100 are not.
- Believing the extra day is added at the end of the year. The leap day is February 29, in the second month, not December 32. A leap year still ends on December 31, it just has one more day in February.
- Confusing leap years with leap seconds. A leap second is a one-off second added to clocks to track tiny changes in Earth rotation. It is unrelated to leap years, which add a whole calendar day.
Glossary
- Leap year
- A year of 366 days that includes an extra day, February 29, to keep the calendar aligned with the Earth orbit around the Sun.
- Common year
- An ordinary year of 365 days with 28 days in February and no February 29.
- Century year
- A year ending in 00, such as 1900 or 2000. These are leap years only when divisible by 400.
- Gregorian calendar
- The calendar in common use worldwide today, introduced in 1582, which sets the modern divisible by 4, 100, and 400 leap year rule.
- Julian calendar
- An earlier calendar that made every fourth year a leap year, which added slightly too many leap days over the centuries.
Frequently asked questions
Is this year a leap year?
Use the This year button to check instantly. As a guide, 2024 was a leap year, 2025 and 2026 are not, and 2028 will be the next one. Leap years fall every four years, skipping most century years.
What is the leap year rule?
A year is a leap year if it is divisible by 4, except century years (ending in 00), which must also be divisible by 400. So 2024 and 2000 are leap years, while 1900 and 2100 are not.
Why is 2000 a leap year but 1900 is not?
Both divide by 4 and both are century years, so both are first set aside by the century exception. But 2000 divides by 400, which makes it a leap year, while 1900 does not divide by 400, so it stays a common year.
How many days are in a leap year?
A leap year has 366 days, one more than the 365 days in a common year. The extra day is February 29, so a leap year has a February of 29 days instead of 28.
When is the next leap year?
Counting from 2026, the next leap years are 2028, 2032, 2036, 2040, and 2044. The tool lists the next five leap years for whatever year you enter.
Why do we have leap years at all?
The Earth takes about 365.2422 days to orbit the Sun, slightly more than 365. Adding a leap day roughly every four years absorbs that extra time and stops the calendar drifting away from the seasons.