The Persian calendar begins on the vernal equinox. It has 12 months, where the first six have 31 days, the next five have 30 days, and the last has either 29 or 30 depending on whether it’s a leap year. One of the longest chronological records in human history, the Iranian calendar has been modified time and again during its history to suit administrative, climatic, and religious purposes.
Iranian year start at the first day of spring on March 21 which in an ancient festival called Norooz. The months in order are: (Spring)Farvardin, Ordibehesht, Khordad (Summer) Tir, Mordad and Shahrivar, (Fall) Mehr, Aban, Azar, (Winter)Day, Bahman and Esfand.
Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses an UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, the same meridian which defines the Iranian calendar and is the official meridian of Iran.
Weeks in Iran start on Saturday and weekends are on friday.
Iran uses three official calendar systems: the Iranian calendar as the main date, the lunar Islamic calendar for religious events, and the Gregorian calendar for international events (like May Day).