Nowrūz (Persian language: نوروز [noʊruːz]), meaning 'New Day') is the traditional ancient Iranianfestival and also the start day of Iranian "New Year".

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.

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The UN's General Assembly in 2010 recognized the International Day of Nowruz, describing it a spring festival of Persian origin which has been celebrated for over 3,000 years. During the meeting of The Inter-governmental Committee for the Safeguarding of the Intangible Heritage of the United Nations, held between 28 September – 2 October 2009 in Abu Dhabi, Nowrūz was officially registered on the UNESCO List of the Intangible Cultural Heritage of Humanity.Since 2010, the United Nations General Assembly recognizes March 21 as the "International Day of Nowruz".

Refrence:www.wikipedia.com