What is Leap Year Definition and When Does Leap Year Occur?
To understand what is meant by leap year and when does leap year occur, we must look at celestial mechanics. While human civil calendars count 365 days in a standard year, the Earth takes approximately 365 days, 5 hours, 48 minutes, and 45 seconds (365.2422 solar days) to complete one orbit around the Sun. Without a periodic calendar adjustment, our calendar would drift out of alignment with the solstices and seasons by roughly 24 days every century!
The 3 Gregorian Leap Year Rules
1. The year must be evenly divisible by 4.
2. If the year can be evenly divided by 100, it is NOT a leap year (e.g. 1900, 2100).
3. Unless the year is also evenly divisible by 400 (e.g. 1600, 2000, 2400).
How Many Days Has a Leap Year?
People frequently ask how many days has a leap year: Standard years have 365 days, whereas leap years boast 366 leapyear days, with February 29 (feb leap year) added to balance the astronomical deficit.