In Islam's calendar it was during the ninth month, Ramadan, that God first began revealing the Quran through the Prophet Muhammad. In the 14 centuries since, Muslims have obeyed the Quran's dictates (2:183-187) and fasted during daylight hours throughout the month.
Ramadan is a period for reflection, self-restraint, prayer, reading the Quran, repenting for one's sins and remembering the poor and hungry.
The last 10 days are regarded as especially holy and some Muslims pray all night. The Lailat al-Qadr, or Night of Power, which occurs on one of the final odd-numbered evenings, marks the point when the Quran was given.
The fasting month is one of Islam's ``five pillars'' or obligatory observances. The others: profession of faith in the one God and Muhammad as his messenger (in Arabic, the shahada); five daily prayers recited in Arabic while facing Mecca (salah); a charitable payment, usually annual (zakat); and at least one pilgrimage to Mecca (hajj) if possible.
During Ramadan, believers abstain from all food, drink, smoking, sex and other pleasures during daylight, which the Quran defines as the hours when a white thread can be distinguished from a black thread. Oral and injected medicines may also be shunned.
Travelers, the sick, and women who are pregnant, nursing or menstruating are allowed to make up fast days later. Younger children and the mentally incapacitated are exempt. So are soldiers and others charged with protecting Muslim lives.
Many Muslims are urging the United States to observe a Ramadan truce in Afghanistan for the month. Historically, Muslims have sometimes but not always halted military action during the holy month.
Normal workday life often slows for Ramadan, especially where temperatures are high or days very long. The Council on American-Islamic Relations asks that U.S. employers and schools give Muslims special consideration on requests for vacation, flexible schedules or lighter homework.
Ramadan also has its festive side. Families and friends who have not eaten since dawn may gather to break the fast with special dishes at the post-sunset meal (iftar).
Since the Muslim calendar is lunar, months are unrelated to the seasons of the sun, and years are shorter than in solar calendars. Ramadan falls back about 11 days a year against today's Western calendar fixed by Pope Gregory XIII in 1582.
Where Christian and Jewish calendars are based on astronomical calculations, the Muslim month officially begins with the visual sighting of the new crescent moon, Islam's symbol. Thus Ramadan's start is not fixed in advance and can vary from country to country.