Zoroastrian practices were dominant for much of the history of ancient Iran. In Zoroastrianism, the seven most important Zoroastrian festivals are the six Gahambar festivals and Nowruz, which occurs at the spring equinox. According to Mary Boyce, “It seems a reasonable surmise that Nowruz, the holiest of them all, with deep doctrinal significance, was founded by Zoroaster himself”; although there is no clear date of origin.