 Intercalation (timekeeping)

Intercalation in timekeeping refers to the insertion of additional time units into a calendar system to ensure that the calendar stays in alignment with the astronomical seasons or the solar year. This is necessary because the length of a solar year is not exactly divisible by the length of a calendar year. For example, a standard calendar year is typically 365 days, but a solar year (the time it takes for the Earth to complete one orbit around the Sun) is about 365.2425 days.