Which calendar system gives the New Year celebration of Nowruz its traditional date near the spring equinox?

The Solar Hijri calendar gives Nowruz its traditional date near the spring equinox.

Nowruz is the Persian New Year and begins at the spring equinox, usually on March 20 or March 21 in the Gregorian calendar. Its date is determined by astronomical calculation within the Solar Hijri, or Iranian, calendar, rather than by a fixed Gregorian date. The celebration marks the start of spring and the beginning of the calendar year.

Nowruz has ancient roots connected with Iranian cultural traditions and is observed across Iran, Afghanistan, Central Asia, the Caucasus, and communities worldwide. Customs include house cleaning, visiting relatives, festive meals, and the haft-sin table, which displays symbolic items beginning with the Persian letter “sin.”

Nowruz is sometimes mistakenly described as a December New Year's Eve celebration because it is a New Year festival. Its defining seasonal setting is different: it welcomes spring in the Northern Hemisphere. UNESCO inscribed Nowruz on its Representative List of the Intangible Cultural Heritage of Humanity in 2009.