Nowrūz means a "New-Day" in Persian and is a new year holiday that begins at the moment of Vernal Equinox (commonly known as the Spring or March Equinox) in West and Central Asia, and the South Caucasus regions (modern day Iran, Afghanistan, Tajikistan, parts of Iraq, Turkey, Syria, Uzbekistan, and other Central Asian nations).
Ancient Persians and peoples of Mesopotamia were keen astronomers, in fact they invented this science because harvest depended on planting crops at the correct time of the year.
The Vernal Equinox occurs when the sun shines directly on the equator. This is an annual celestial phenomenon that marks the start of Spring (around 20-21 March) in the northern hemisphere.
Originally an ancient holiday celebrating the coming of Spring, a time of rebirth and fertility. Nowruz has lent many of its features to Christian and Judiac Spring celebrations such as Easter and Passover! Throughout the millennia, Nowruz has borrowed from Zoroastrian and Muslim traditions.