Wikipedia - Nowrūz is the traditional Iranian new year holiday celebrated in Iran, Turkey, Azerbaijan, Afghanistan, Albania, Armenia, Georgia, the countries of Central Asia such as Turkmenistan, Tajikistan, Uzbekistan, Kyrgyzstan, and Kazakhstan, as well as among various other Iranian and Turkic people in Iraq, Syria, Lebanon, Pakistan, India, Northwestern China, the Caucasus, the Crimea, and the Balkans.
Nowruz marks the first day of spring and the beginning of the Iranian year as well as the beginning of the Bahá'í year. It is celebrated on the day of the astronomical vernal equinox (start of spring in northern hemisphere), which usually occurs on the March 21st or the previous/following day depending on where it is observed.
As well as being a Zoroastrian holiday, it is also a holy day for adherents of Sufism as well as Bahá'í Faith. In Iran it is also referred to as an Eid festival, although it is not an Islamic feast. Shia Nizari Ismaili muslims, who trace their origins to Iran, celebrate the festival under the name Navroz. In their religious protocol, Navroz is officially recognized as an Eid, as with Eid ul-Fitr and Eid ul-Adha, although it involves a distinct set of religious ceremonies. Alawites also celebrate Nowruz.
The term Nooroz first appeared in Persian records in the second century AD, but it was also an important day during the time of the Achaemenids (c. 648-330 BC), where kings from different nations under the Persian empire used to bring gifts to the emperor of Persia on Nowruz.