Ramadan

Ramadan is a month when adult Muslims are required to fast. The fast begins each day at dawn and goes until sunset. Muslims are forbidden to eat, drink, and smoke during this time. It occurs during the ninth month of the Islamic year, which was chosen because it was the first month that the prophet Muhammed recieved his first revelation from Allah, the Islamic God.

Source: http://library.thinkquest.org/28505/islam/ramad.htm