A leap year, also known as an intercalary year or bissextile year, is a year that contains an extra day. This additional day, February 29th, is inserted into the calendar in order to synchronize the calendar year with the solar year, or the length of time it takes for the Earth to complete its orbit around the sun.

The standard calendar year is 365 days long, but the Earth's orbit around the sun actually takes about 365.2422 days. To account for this discrepancy, an extra day is added to the calendar approximately every four years, creating a leap year. This adjustment helps keep the calendar year in alignment with the astronomical year, preventing the seasons from gradually drifting out of sync with the calendar.

Key points about leap years:

• Frequency: Leap years occur every four years. However, to maintain accuracy, some exceptions are made to this rule.

• Exceptions: Years divisible by 100 are not leap years unless they are also divisible by 400. For example, the year 1900 was not a leap year, but the year 2000 was.

• Duration: A leap year has 366 days instead of the usual 365. The additional day is added to the month of February.

• History: The concept of a leap year has ancient origins, with various cultures attempting to synchronize their calendars with the solar year. The introduction of leap years is often credited to the Roman general and statesman Julius Caesar, who implemented the Julian calendar in 45 BCE.

Leap years play a crucial role in maintaining the accuracy of our calendars and ensuring that seasonal changes occur at approximately the same time each year. Without the addition of leap days, over time, our calendars would drift out of sync with the Earth's orbit around the sun.