The first day of the Iranian calendar falls on the March equinox, the first day of spring, around 21 March. In the 11th century AD, the Iranian calendar was reformed in order to fix the beginning of the calendar year, i.e. Nowruz, at the vernal equinox. Accordingly, the definition of Nowruz given by the Iranian astronomer Tusi was the following: “The first day of the official New Year [Nowruz] was always the day on which the sun entered Aries before noon.”Nowruz is the first day of Farvardin, the first month of the Iranian solar calendar, which is the official calendar in use in Iran, and formerly in Afghanistan.
