The world's 1 billion Muslims will observe Ramadan by abstaining from food, drink, smoking, and marital relations during daylight hours during the 30-day long period of abstinence and purification. The holy month marks God's revelation of the holy book, the Koran, to the Prophet Mohammed 1,400 years ago, according to Islamic belief.
The starting date of Ramadan changes each year and is begun with the sighting of the new moon. It ends 29 or 30 days later when the next new moon is seen and culminates with the three-day feast of Eid al-Fitr.