Why is there an extra day added to February very four years?

An extra day is added to February every four years to account for the fact that a year is not exactly 365 days long; it's approximately 365.25 days. This discrepancy is resolved by designating February 29 as a leap day in leap years, which helps align the calendar year with the astronomical year. Without this adjustment, our calendar would gradually drift out of sync with the seasons over time.