Ashura is the 10th day of Muharram which marks the day when Imam Hussein (PBUH) and his companions were martyred at the Battle of Karbala.
The day of Ashura is the 10th day of Muharram in the Lunar Hijri calendar. This day is significant for Shia due to what occurred in Karbala on this day in the year 61 AH (October 10, 680 CE). On that day, Imam Hussein (PBUH) and his true companions were martyred in the battle against the Kufa army led by ‘Umar b. Sa’d.
Every year with the advent of Muharram, Shi’a around the world hold mourning ceremonies for Imam Hussein, which usually continue to the 11th or 12th of Muharram and, in some regions, to the end of the month of Safar (the following month). The day of Ashura is the climax of the mourning and is an official holiday in Iran, Iraq, Afghanistan, Pakistan, and India.