Nowruz marks the first day of spring and the beginning of the year in the Iranian/Persian calendar. It is celebrated on the day of the astronomical Northward equinox, which usually occurs on March 21 or the previous/following day depending on where it is observed.
The UN recognizes the International Day of Nowruz, as an over 3000 year spring Iranian/Persian festival.
سال نو بر همه مبارک! نوروزتان پیروز