Calendopaedia - The Persian Calendar

The Persian calendar was introduced in Persia in 1925 and is used to this day in Iran and Afghanistan. It is a solar calendar with 12 months and either 365 or 366 days. The leap year cycle is 2820 years long with 683 leap years during the cycle. This gives a year length of 365.2422 days, which gives a very accurate calendar indeed. For comparison the Gregorian leap year cycle is 400 years long.

The 2820 year cycle is divided into 21 periods of 128 years followed by a period of 132 years.

Each 128 year period is divided into four periods, one of 29 years and three of 33 years.

The 132 year period is made up of a period of 29 years, then two periods of 33 years followed by one of 37 years.

Within each period every fourth year is a leap year with the count resetting to one every time a new period starts.

The calendar is deemed to have started on 21st March 622 AD (Gregorian). The year starts on 21st or 22nd of March, depending on the relationship with the Gregorian calendar at that time. The months in each year are named as follows. Farvardin, Ordibehesht, Khordad, Tir, Mordad and Shahrivar each having 31 days; Mehr, Aban, Azar, Dey and Bahman each having 30 days and Esfand having 29 days or 30 in a leap year.

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