Final answer:
Nowruz is the festival that celebrates the Persian New Year and takes place on March 21, coinciding with the spring equinox.
Step-by-step explanation:
The festival that marks the beginning of the Persian New Year is Nowruz, which occurs on the spring equinox, March 21. This celebration has its origins in the ancient traditions of the Persian Empire and is a time for renewal and rejoicing among individuals of Persian descent and in many countries across Central Asia and the Middle East. Although the Persian calendar counts the years starting from the Prophet Mohammed's migration to Medina, the New Year itself is celebrated according to the solar calendar, heralding the start of spring.