What Is a Leap Year?
A leap year is a calendar year that contains one extra day — February 29 — making it 366 days long instead of the usual 365. Leap years exist to keep our human calendar aligned with the astronomical year: the time it takes Earth to complete one full orbit around the Sun.
Why Do We Need Leap Years?
Earth's orbital period is approximately 365.2422 days — not exactly 365. A calendar of exactly 365 days would fall short by about 5 hours, 48 minutes, and 45 seconds each year. Over time this error accumulates:
| Time Period | Calendar Drift (without leap years) |
|---|---|
| 4 years | ~1 day behind |
| 100 years | ~24 days behind |
| 400 years | ~97 days behind |
Without the correction, seasons would slowly drift through calendar months — midsummer would eventually arrive in December for the Northern Hemisphere.
The Leap Year Formula (Gregorian Calendar)
- The year is divisible by 4, AND
- The year is NOT divisible by 100 — UNLESS
- The year is divisible by 400
Examples
| Year | ÷4? | ÷100? | ÷400? | Leap Year? |
|---|---|---|---|---|
| 2024 | Yes | No | — | Yes |
| 2025 | No | — | — | No |
| 2026 | No | — | — | No |
| 2028 | Yes | No | — | Yes |
| 2100 | Yes | Yes | No | No |
| 2000 | Yes | Yes | Yes | Yes |
Leap Years 2020–2040
Here are all upcoming leap years for the next two decades:
2020, 2024, 2028, 2032, 2036, 2040
Non-leap years 2025, 2026, 2027 all have 365 days and February has 28 days.
Frequently Asked Questions
Is 2026 a leap year?
No. 2026 is not divisible by 4 (2026 ÷ 4 = 506.5), so it is not a leap year. February 2026 has 28 days and the year has 365 days total. The most recent leap year was 2024, and the next is 2028.
When is the next leap year?
The next leap year is 2028. It is divisible by 4 (2028 ÷ 4 = 507), not divisible by 100, so it qualifies as a full leap year. February 2028 will have 29 days.
What happens to people born on February 29?
People born on February 29 (called "leaplings") legally celebrate their birthday on February 28 or March 1 in non-leap years, depending on local law and personal preference. Some leaplings celebrate both days. About 5 million people worldwide were born on February 29.
Is 2100 a leap year?
No. 2100 is divisible by 100 but NOT by 400, so it is skipped. This is the "century rule" exception. The last century year that was a leap year was 2000 (divisible by 400). The next will be 2400.
How accurate is the Gregorian calendar after adding leap years?
The Gregorian correction (97 leap years per 400-year cycle) brings the average year to 365.2425 days. Earth's actual tropical year is 365.2422 days. The remaining error is about 1 day in every 3,030 years — far more accurate than any practical need.
Did the Julian calendar have leap years?
Yes, but simpler ones. The Julian calendar added a leap day every 4 years without exception — including century years. This led to a drift of about 3 days every 400 years, which accumulated to 13 days by 1582 when Pope Gregory XIII corrected it with the Gregorian calendar rules still used today.