Mandaean calendar

The Mandaean calendar is used by the Mandaean people, an ancient religious group in the Middle East. It has 12 months, and each month has 29 or 30 days. At the end of the year, a 13th month (called Intercalation Month) is added to make up the rest of the days. The calendar is based on the phases of the moon, and it is used to plan different religious ceremonies and festivals.