Why Do We Have Leap Years?

The Origin of Leap Years00:00:00

A year is not exactly 365 days, but rather 365.25 days. Leap years are necessary to reconcile our calendar with the Earth's actual orbital period.

Solar vs. Sidereal Days00:00:43

A solar day is 24 hours based on the sun's position, while a sidereal day, measured against distant stars, is approximately 23 hours and 56 minutes. The 4-minute difference occurs because the Earth moves in its orbit while rotating.

Calendar Adjustments and Precession00:01:33

To keep seasons aligned, we use a complex system of leap years, skipping them every 100 years unless the year is divisible by 400. Additionally, the Earth's axial precession means we must use tropical years to prevent seasonal shifts.