Iranian women pray at the shrine of Saint Qassem on the first day of the Muslim holy fasting month of Ramadan in northern Tehran, Iran, on July 21. Over a billion Muslims around the world have begun observing the holy month of Ramadan, expected to abstain during daylight hours from food, drink and smoking to focus on spirituality. Ramadan starts with the sighting of the new moon, but it varies because Muslim countries and groups use different ways of calculating when the new moon crescent is sighted. (Vahid Salemi/Associated Press) #