What is a leap year?
A leap year is a calendar year that contains 366 days instead of the standard 365. The extra 24 hours are added to the end of February as February 29 (often called "leap day").
Leap years are necessary because the Earth takes approximately 365.2422 days (about 365 days, 5 hours, 48 minutes, and 45 seconds) to complete a full orbit around the Sun. Adding an extra day every four years corrects for this extra fraction of time, keeping our calendar synchronized with astronomical seasons and equinoxes.
Leap Year Calculation
Learning how to calculate leap year rules comes down to three sequential checks under the Gregorian calendar system:
- Step 1: Check division by 4. If the year is evenly divisible by 4, proceed to Step 2. Otherwise, it is a standard 365-day year.
- Step 2: Check division by 100. If the year is divisible by 4 but not divisible by 100, it is a leap year. If it is divisible by 100 (a century year), proceed to Step 3.
- Step 3: Check division by 400. If a century year is evenly divisible by 400, it is a leap year. If not, it is a standard year.
(Year % 4 === 0 AND Year % 100 !== 0) OR (Year % 400 === 0) Leap years in this range
Between 1970 and 2080, there are 28 leap years. Each one includes February 29.
| Year | Days in Year | Days in February |
|---|---|---|
| 1972 | 366 days | 29 days |
| 1976 | 366 days | 29 days |
| 1980 | 366 days | 29 days |
| 1984 | 366 days | 29 days |
| 1988 | 366 days | 29 days |
| 1992 | 366 days | 29 days |
| 1996 | 366 days | 29 days |
| 2000 | 366 days | 29 days |
| 2004 | 366 days | 29 days |
| 2008 | 366 days | 29 days |
| 2012 | 366 days | 29 days |
| 2016 | 366 days | 29 days |
| 2020 | 366 days | 29 days |
| 2024 | 366 days | 29 days |
| 2028 | 366 days | 29 days |
| 2032 | 366 days | 29 days |
| 2036 | 366 days | 29 days |
| 2040 | 366 days | 29 days |
| 2044 | 366 days | 29 days |
| 2048 | 366 days | 29 days |
| 2052 | 366 days | 29 days |
| 2056 | 366 days | 29 days |
| 2060 | 366 days | 29 days |
| 2064 | 366 days | 29 days |
| 2068 | 366 days | 29 days |
| 2072 | 366 days | 29 days |
| 2076 | 366 days | 29 days |
| 2080 | 366 days | 29 days |
Leap years are especially important when calculating an exact age. Use our Age Calculator to include leap days automatically.
Frequently asked questions
Why do we have leap years?
They help keep the calendar aligned with the Earth's orbit around the Sun.
When was the last leap year?
The last leap year was 2024. It had 366 days and included February 29, 2024.
Is 2026 a leap year?
No. 2026 is not a leap year.
Is 2027 a leap year?
No. 2027 is not divisible by 4, so it is a standard year with 365 days and 28 days in February.
When is the next leap year?
The next leap year is 2028, followed by 2032 and 2036.
Why are century years like 1900 not leap years?
Adding a leap day every 4 years overcompensates slightly because the Earth's orbit is a bit shorter than 365.25 days. Skipping century years unless they are divisible by 400 (like 2000) keeps the calendar perfectly precise.