Sadeh Sadeh is a mid-winter celebration observed by Iranians from the ancient time. The bonfire is to drive back the winter in defiance of Ahriman. Sadeh has a complex history, and two different traditions are to be noted. By Yazd tradition, it is observed on Ashtad ruz, Azar Mah. According to the Fasli calendar, this would place it on Dec 11.
People begin to gather an hour before sunset, a spot near a stream seems to be preferred.
Although it is mentioned in the Qissa-i Sanjan, Sadeh does not seem to have much significance among modern Parsi Zoroastrians. He says the fire is to symbolize the approach of winter which necessitates the kindling of fires. The Iranian Sadeh, which means hundred, is a mid-winter feast that was celebrated with grandeur and magnificence in ancient Iran. Two different days were observed for its veneration. One celebration marked the hundredth day before the religious Norooz on the first day of the Farvardin, or March 21.