Muharram 2018 marks the start of Islamic New Year, and is a key month in the Islamic calendar.
The dates differ each year as the Islamic and Gregorian calendars are not in sync. In 2018, Muharram will be observed from September 11 - October 9.
Last year it began on September 21, and in 2016 it started on October 2. This happens because the Islamic calendar is based on the lunar cycle, while the Gregorian calendar follows the rising and setting of the sun.
Muslims of shia sect, in black attire, participate in the gatherings in which the sacrifices of Hussein and his companions are commemorated. Hussein, the grandson of Prophet Muhammad, was martyred in 680 AD by a group of 72 men, women and children in the harsh terrain of Karbala.
Islamic New Year begins with the sighting of the new moon at sunset. This occurs on the final day of Dhu al-Hijjah, the last month of the Islamic Calendar. In 2018, this falls on September 10.