Iran uses three official calendar systems, including the Persian calendar (Solar) as the main and national calendar, the Gregorian calendar for international events and Christian holidays, and the Lunar calendar for Islamic holidays.
The surfeit of public holidays has been a subject of concern for almost 30 years. A substantial number of unofficial holidays are added each year to the national holidays that further aggravate the situation.
Iran has the most public holidays in the world with around 25 holidays. The holidays in Iran may differ regarding the Arabic Calendar.[1][2]
References
Public holidays in Iran Wikipedia(Text) CC BY-SA