Naw-Ruz is the Bahá'í and Iranian new year, which occurs on the date of the vernal equinox, about 21 March. It is one of the nine Bahá'í holy days on which work is suspended. I still worked yesterday, though.
Naw-Ruz in Iran probably began as a pastoral fertility festival--it's still celebrated as one of the two important annual festivals of Zorastrianism. The other is Ihrajan, held on the autumnal equinox in September.