Ramadan[a][note 1] is the ninth month of the Islamic calendar. It is observed by Muslims worldwide as a month of fasting (sawm), communal prayer (salah), reflection, and community.[5] It is also the month in which the Quran is believed to have been revealed to the Islamic prophet Muhammad. The annual observance of Ramadan is regarded as one of the five pillars of Islam[6] and lasts 29 to 30 days, from one sighting of the crescent moon to the next.