A leap year is an additional year added to the traditional calendar year in order to synchronize the calendar year with the astronomical year, which is the time it takes for the Earth to complete one orbit around the Sun. The concept of a leap year has been in use for centuries, and its calculation has evolved over time. The modern leap year system was introduced by Julius Caesar in 45 BC as part of his calendar reform. The Julian calendar, as it came to be known, added an extra day to the month of February every four years. This adjustment brought the average length of a calendar year to 365.25 days, which is very close to the length of an astronomical year. However, the Julian calendar was not entirely accurate, as it resulted in a drift of approximately three days every four centuries. This discrepancy became apparent during the 16th century, when Pope Gregory XIII commissioned a group of mathematicians and astronomers to devise a more precise calendar system. The result was the Gre...