Nowruz (Persian: Nowruz – [nouˈɾuːz]; literally "New Day") is the name of the Iranian New Year.

Although having Iranian and religious Zoroastrian (Zardashti) origins, Nowruz has been celebrated by people from diverse ethno-linguistic communities for thousands of years. It is a secular holiday for most celebrants that is enjoyed by people of several different faiths, but remains a holy day for Zoroastrians  زردشت Zardasht

Origin

Nowruz is partly rooted in the religious tradition of Iranian religions such as Zoroastrianism (Zardasht) or even older in tradition of Mitraism .... The Persian festivals of Yalda (longest night) and Mehregan )(autumnal equinox) and Tiregān (longest day) also had an origin in the Sun god (Surya.

Before the collapse of the Soviet Union, Iran was the only country that officially observed the ceremonies of Nowruz.

The UN's General Assembly in 2010 recognized the International Day of Nowruz, describing it as a spring festival of Persian origin which has been celebrated for over 3,000 years.

Along with Ismailis shias, Alawites and Alevis, the Twelver Shi’a also hold the day of Nowruz in high regard.

The day also assumes special significance for Shias as it was on 21 March 656 AD when , Ali, assumed the office of Caliphate.

The holiday is considered by Kurds to be the single most important holiday of every year. With this festival Kurds gather into the fairgrounds mostly outside the cities to welcome spring. Women wear colored dresses and spangled head scarves and young men wave flags of green, yellow and red, the colors of the Kurdish people. They hold this festival by lighting fire and dancing around it.

(Wikipedia)