Zarthost No Deeso usually occurs in June, on Khorshed roz, Dae mah (11th day, 10th month) as per the Zoroastrian calendar. This is the day on which the death anniversary of Prophet Zoroaster symbolically falls. Special prayers are recited and Zoroastrians go to the Fire Temple to pray. There aren't any elaborate celebrations on the day, since it is a solemn occasion. There are many versions of the legend of how Zarathustra died. One says that in his 77th year, he was killed in a fire-temple by the Turanian army. A variation says that the person who was killed was not Zarathustra, but someone else while Zarathustra himself ascended the skies.
There are also versions which say that the murderer was also killed on the spot by divine intervention, or that Zarathustra was killed by a thunderbolt. Another legend says that Zarathustra died in his sleep. There are no public functions to mark the day. Ceremonies and services are confined to either the home or to the temple. Special prayers are recited, and lectures and discourses are held on the life and works of the prophet. Zarthost No Deeso is highly observed in Mumbai and Gujarat particularly, and in other parts of India which have a considerable Parsi population.