Zartosht No-Diso is a Zoroastrian holy day that commemorates the death anniversary of the prophet Zoroaster (Zarathushtra). It is observed on the 11th day of the 10th month (Khorshed Dae) of the Zoroastrian calendar. On this day, Zoroastrians remember Zoroaster's teachings and conduct special prayers at fire temples, reflecting on his message of good thoughts, good words, and good deeds.