Here's a breakdown:
* Earth's Orbit: The Earth takes approximately 365.2422 days to orbit the sun.
* Calendar Year: Our standard calendar year has 365 days.
* The Discrepancy: This means that our calendar year is about 0.2422 days (almost a quarter day) shorter than Earth's actual orbital period.
* Leap Years: To account for this discrepancy, we add an extra day (February 29th) every four years, creating a leap year with 366 days. This helps keep our calendar year aligned with the seasons.
The 400-Year Rule:
However, the simple 4-year rule isn't perfect. To make things even more accurate, there is a 400-year rule:
* Centuries are not leap years unless divisible by 400. This means that years like 1700, 1800, and 1900 were not leap years, even though they are divisible by 4. However, 2000 was a leap year because it is divisible by 400.
In summary:
We don't get a leap year every four years. Rather, we *add* a leap day every four years (except for century years not divisible by 400) to keep our calendar year aligned with Earth's actual orbital period.
