A leap year is not simply every fourth year. The Gregorian rule has three parts: a year divisible by 4 is a leap year, unless it is divisible by 100, unless it is also divisible by 400. That is why 1900 was an ordinary year of 365 days while 2000 had 366, a distinction that broke a great deal of software written in the 1990s.
2026 is not a leap year, so February has 28 days and the year runs to 365 days. The next three leap years are 2028, 2032 and 2036. The calculator names which part of the rule decided the answer rather than just returning yes or no.
The correction exists because the Earth takes about 365.2422 days to orbit the Sun. Adding a day every four years overshoots slightly, so the century exceptions pull the average back to 365.2425 days, leaving an error of roughly one day in 3,200 years.
The formula
Y- The year being tested
Feb- Length of February in that year
DIY- Total days in the year
How it works, step by step
- Enter any year, past or future.
- The gauge shows the number of days in that year.
- Read whether it is a leap year and which rule decided it.
- The next leap years are listed for planning ahead.
Worked examples
Is 2026 a leap year?
2026 divided by 4 leaves 2, so it fails the first test and is a common year of 365 days. February 2026 has 28 days. The next leap year is 2028, which is 2 years away.
The century exception
1900 is divisible by 4 but also by 100 and not by 400, so it had 28 days in February. 2000 is divisible by 400, so it had 29. Between 1900 and 2000 there were 25 leap years, not 25.
How to read your score
Frequently asked questions
Why is every fourth year not enough?
Because the tropical year is about 365.2422 days, slightly less than 365.25. Adding a day every four years gains roughly three days every four centuries, which the century rule removes.
Was 1900 a leap year?
No. It is divisible by 100 but not by 400, so February 1900 had 28 days. Many spreadsheets still model 1900 as a leap year for backwards compatibility with early software.
How many leap years are in 400 years?
97. That gives an average year of 365.2425 days across the cycle.
Does the rule work for years before 1583?
Not reliably. The Gregorian calendar was introduced in 1582 and adopted at different times in different countries, so earlier dates follow the Julian rule of every fourth year with no exceptions.
When is the next century year that is a leap year?
2400. 2100, 2200 and 2300 are all skipped because none divides by 400, so there is a gap of eight years between the leap years of 2096 and 2104.
Leap year reference
| Year | Divisible by 4 | Divisible by 100 | Divisible by 400 | Days in February |
|---|---|---|---|---|
| 1900 | yes | yes | no | 28 |
| 1996 | yes | no | no | 29 |
| 2000 | yes | yes | yes | 29 |
| 2024 | yes | no | no | 29 |
| 2025 | no | no | no | 28 |
| 2026 | no | no | no | 28 |
| 2100 | yes | yes | no | 28 |
| 2400 | yes | yes | yes | 29 |
Only 2000 and 2400 pass the century test; 1900 and 2100 are ordinary years.