The first month of the Solar Hijri calendar, Farvardin, has 31 days.
Farvardin is the first month of the Iranian Solar Hijri calendar and begins with Nowruz, around the March equinox. Its 31-day length places the start of the calendar’s first month in spring and carries it into April in the Gregorian calendar. The month is followed by Ordibehesht, the second month.
The Solar Hijri calendar uses a regular pattern for its months. The first six months, from Farvardin through Shahrivar, each contain 31 days. The next five months contain 30 days, while Esfand, the twelfth month, has 29 days in an ordinary year and 30 in a leap year. This pattern differs from the Gregorian calendar, where month lengths alternate irregularly.
Farvardin does not always align with exactly the same Gregorian dates. In most years it begins on 21 March, but astronomical timing and leap-year adjustments can place its first day on 20 March, and very rarely on 19 or 22 March. Its final day therefore also shifts slightly against the Gregorian calendar.