Calendar Systems & Timekeeping
Intercalation
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<holidayfyi-glossary slug="intercalation"></holidayfyi-glossary>The insertion of an extra day, week, or month into a calendar to reconcile it with the solar year or astronomical cycles. The Gregorian leap day (February 29) and the Hebrew leap month (Adar II) are examples of intercalation. Without intercalation, lunar calendars would drift through all seasons over time, and harvest festivals would eventually fall in winter.