What happens every 4 years on Earth?

The Earth revolves around the Sun in approximately 365.25 days, completing a full cycle known as a solar year. This duration is slightly longer than the standard 365 days we use in our calendar years.

To compensate for the fractional day missing from each calendar year, a corrective measure is employed to ensure the accuracy of our timekeeping. This adjustment is achieved by introducing an additional day into our calendar at specific intervals.

Specifically, a leap year is declared every four years. This leap year includes an extra day, February 29th, which is not present in common years. This extra day serves to align our calendar years more closely with the actual duration of a solar year.

The concept of leap years originated as a way to synchronize the Gregorian calendar, which is widely used today, with the astronomical events that occur within a solar year. By doing so, the calendar can better reflect the seasonal changes and celestial movements observed throughout the year.

The decision to include a leap year is based on the understanding that the Earth's orbit around the Sun is not perfectly circular but slightly elliptical. This results in slight variations in the duration of each orbit, necessitating the use of leap years to maintain the accuracy of our timekeeping system.