From Wikipedia:
Nowrūz (Persian language: نوروز [noʊruːz]), meaning 'New Day') is the traditional ancient Iranian[1] new year festival and also the start day of the Iranian new year. As the European historical name of Iran is Persia, Nowruz is widely referred to as Persian New Year too.[2][3][4][5]Nowruz is celebrated and observed by Iranian peoples and the related cultural continent and has spread in many other parts of the world, including parts of Central Asia, South Asia, Northwestern China, the Crimea and some ethnic groups in Albania, Bosnia, Serbia and the Republic of Macedonia.
Nowruz marks the first day of spring and the beginning of the year in Iranian calendar. It is celebrated on the day of the astronomical vernal equinox, which usually occurs on March 21 or the previous/following day depending on where it is observed. As well as being a Zoroastrian holiday and having significance amongst the Zoroastrian ancestors of modern Iranians, the same time is celebrated in the Indian sub-continent as the new year. The moment the Sun crosses the celestial equator and equalizes night and day is calculated exactly every year and Iranian families gather together to observe the rituals.
Nowruz was originally a Zoroasterian festival, and holiest of all, and as such has unclear date of origin...
well, like the saying goes, “you learn something new every day.”