Muharram (Arabic (Arabic language): langar????) is the first month of the Islamic calendar. It is one of the four sacred months of the year in which fighting is prohibited. Since the Islamic calendar is lunar, Muharram moves from year to year when compared with the Gregorian calendar. Muharram is so called because it is unlawful to fight during this month; the word is derived from the word haram (Haraam), meaning "forbidden". It is held to be the most sacred of all the months, excluding Ramadan. Some Muslims fast during these days. The tenth day of Muharram is called Yaumu-l Ashurah, which is known by Shia Muslims as ?the day of grief?. Fasting differs among the Muslim groupings; mainstream Shia Muslims stop eating and drinking during sunlight hours and do not eat until late afternoon. Sunni Muslims also fast during Muharram for the first 10 days of Muharram or on the tenth day or on both the 9th and 10th days, the choice is up to the individual. Shia Muslims do so to replicate the sufferings of Imam Hussain (A.S) on the day of Ashurah.