What astronomical event marks the beginning of Nowruz?

The vernal equinox marks the beginning of Nowruz.

Nowruz is the Persian New Year and begins at the precise astronomical moment of the March equinox, when day and night are approximately equal in length. In the Northern Hemisphere, this event marks the beginning of spring, which explains the festival’s strong themes of renewal, growth and fresh beginnings.

Unlike a fixed civil holiday that always begins at midnight, Nowruz begins at the equinox itself. The exact time varies from year to year and determines when celebrations start in different time zones. The holiday is then observed through customs that may continue for several days or weeks.

Nowruz has roots in Iranian cultural history and is celebrated across Iran and by communities in many neighboring countries, including Afghanistan, Azerbaijan, parts of Central Asia and Iraqi Kurdistan. The winter solstice and summer solstice are also astronomical turning points, but neither marks the start of Nowruz.