Why Do We Have Leap Years?
The Earth completes an orbit around the Sun in approximately 365.2422 solar days. Because a standard calendar year is only 365 days, without an adjustment, our calendar would drift by about 1 day every 4 years, eventually displacing seasons.
The Three Rules of the Gregorian Calendar
1. Every year divisible by 4 is a leap year. 2. However, years divisible by 100 are NOT leap years. 3. Exception to the exception: years divisible by 400 ARE leap years. This is why 2000 was a leap year, but 1900 was not, and 2100 will not be.
Leap Year Birthdays
People born on February 29 (known as leaplings) officially celebrate on February 28 or March 1 in common years. For software calculations, our system provides deterministic mapping to February 28 for consistency.