Leap Year Calculator
Check if any year is a leap year, find the next and previous leap years, and count how many leap years fall between two dates.
What Makes a Year a Leap Year?
The Gregorian calendar adds a 366th day — February 29 — to years that are divisible by 4, except century years (1800, 1900, 2100), which must also be divisible by 400 to qualify. So 2000 was a leap year (400 ÷ 400 = 5), but 1900 was not (1900 ÷ 400 = 4.75). The rule exists because the solar year is approximately 365.2422 days — without leap years, the calendar would drift about 1 day every 4 years, misaligning seasons over centuries.
Leap Year Rule Summary
Divisible by 4? → Leap year. Unless divisible by 100 → Not a leap year. Unless also divisible by 400 → Leap year. The formula in code: year % 4 == 0 && (year % 100 != 0 || year % 400 == 0).
People Born on February 29
People born on February 29 (called "leaplings") celebrate their birthday on February 28 or March 1 in non-leap years, depending on the country and personal preference. Statistically, the chance of being born on a leap day is about 1 in 1,461 — there are approximately 5 million leap day birthdays worldwide.