The tabular Islamic calendar, used in Iran, has 12 lunar months that usually alternate between 30 and 29 days every year, but an intercalary day is added to the last month of the year 12 times in a 33-year cycle. Some historians also linked the pre-Islamic practice of Nasi' to intercalation.
The tabular Islamic calendar used in Iran has 12 lunar months that usually alternate between 30 and 29 days every year but an intercalary day is added to the last month of the year 12 times in a 33-year cycle Some historians also linked the pre-Islamic practice of Nasi' to intercalation