Leap years are years that have an extra day added to them, specifically February 29th. This adjustment is made to keep our calendar in alignment with the Earth’s revolutions around the Sun. A leap year occurs every four years, with some exceptions.
To determine how many leap years have occurred, we follow these rules:
- A year is a leap year if it is divisible by 4.
- However, if the year can be evenly divided by 100, it is not a leap year, unless…
- The year is also divisible by 400, in which case it is a leap year.
For example, the year 2000 was a leap year because it is divisible by 400, while 1900 was not because it is divisible by 100 but not by 400.
As of October 2023, we can calculate the leap years from the year 1 AD to 2023 AD. The total number of leap years can be found using the above rules, and it generally amounts to roughly 1 leap year every 4 years, giving a rough estimate. For precise counting, you would account for the exceptions based on century years and those divisible by 400.