Muharram, the first month of the Islamic calendar, bears importance for Shia Muslims because of the martyrdom of Hussein Ibn Ali, Mohammed's grandson, during the month. Some Sunni Muslims fast during the month in observance of the Mourning of Muharram, which commemorates the Battle of Karbala in 680 C.E.
Muharram, one of four sacred months in the Islamic year, is generally perceived as second in importance only to Ramadan. Due to differences between the Islamic and Gregorian calendars, the month occurs at different times each year in the Gregorian calendar.
Sunni traditions also consider the month important because the Moses and the Israelites triumphed over the Pharoah of Egypt on 10th day of the month. Many Sunni Muslims fast on the 9th and 10th days of Muharram in observance of this event.