Mehregan is an Iranian festival honoring the Zoroastrian
yazata Mithra. Under the
Achaemenid Empire (550–330 BC), the
Armenian subjects of the Persian king gave him 20,000 horses every year during the celebration of Mehregan. Under the
Sasanian Empire (224–651), Mehregan was the second most important festival, falling behind
Nowruz. Due to these two festivals being heavily connected with the role of Iranian kingship, the Sasanian rulers were usually crowned on either Mehregan or Nowruz. In
Biruni's eleventh-century
Book of Instructions in the Elements of the Art of Astrology (233), the astronomer observed that "some people have given the preference to Mihragān [over Nowruz, i.e. New Year's day/Spring Equinox] by as much as they prefer autumn to spring." As Biruni also does for the other festival days he mentions, he reiterates a local anecdotal association for his description of Mehregan with a fragment of a tale from Iranian folklore: On this day,
Fereydun vanquished the evil
Zahhak and confined him to
Mount Damavand. This fragment of the legend is part of a greater cycle that ties Mehrgan with Nowruz; Dahak vanquished
Jamshid (who the legends have as the one establishing Nowruz or New Year's Day), and Fereydun vanquishes Zahhak, so restoring the balance. The association of Mehregan with the polarity of spring/autumn, sowing/harvest and the birth/rebirth cycle did not escape Biruni either, for as he noted, "they consider Mihragān as a sign of resurrection and the end of the world, because at Mihragān that which grows reaches perfection." ==In ancient times==