Solar calendars

Solar calendars are systems of timekeeping that are based on the position of the Earth in relation to the Sun. In a solar calendar, a year is defined as the time it takes for the Earth to complete one full orbit around the Sun, which is approximately 365.25 days. To account for the fractional days, most solar calendars include a system for leap years, which adds an extra day (February 29) every four years in order to keep the calendar year synchronized with the astronomical year.