A leap year has 366 days, with a 29th day added to February. Under the Gregorian rule a year is a leap year if it's divisible by 4 — except century years (divisible by 100), which are leap years only if they're also divisible by 400. This calculator shows the verdict, the reason, the days in the year and February, and the next leap year.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: Gregorian leap-year rule, recomputed in code.
The rule
Most years that divide evenly by 4 are leap years. The exception is the turn of a century: 1700, 1800, 1900 and 2100 are not leap years even though they divide by 4, because they divide by 100 but not 400. Years like 1600, 2000 and 2400 are leap years, because they divide by 400. The correction keeps the calendar accurate to the Earth's orbit over centuries.
Worked examples
2024:
1900 vs 2000 (century years):
2100:
So 2024 and 2000 are leap years, while 1900 and 2100 are common years of 365 days. After a non-leap century like 2100 the next leap year is just 2104.
Frequently Asked Questions
Divisible by 4, except centuries not divisible by 400. 2024 & 2000 leap; 1900 & 2100 not.
No — ÷100 but not ÷400, so it's a common year. Next century leap year is 2400.
Earth's orbit is ~365.2422 days. Feb 29 every ~4 years absorbs the extra quarter-day.
366 — one more than 365. February has 29 days instead of 28.
Someone born Feb 29. They usually celebrate on Feb 28 or Mar 1 in common years.