Jashn e Nowruz

Details:

The first day of the Iranian calendar falls on the March equinox, the first day of spring, around March 21. In the 11th century CE 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 scientist 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.