They observe the 10th of Muharram, the day of `Ashura, as a day of public mourning.
On the 11th of Muharram 656 (January 1258) Hulaku arrived under the walls of the capital.
Hosain gave battle, vainly relying on the promised aid from Kufa, and fell with almost all his followers on the 10th of Muharram 61 (loth of October 680).
The era begins from the first day of the month of Muharram preceding the flight, or first day of that Arabian year which coincides with Friday, July 16, 622 A.D.
Muharram 1, New Year.