Fasting during the month of Ramadan is one of the Five Pillars of Islam. The month is spent by Muslims fasting during the daylight hours from dawn to sunset. Muslims believe that the Quran was sent down to the lowest heaven during this month, thus being prepared for gradual revelation by Jibraeel (Gabriel) to the Islamic prophet Muhammad. Furthermore, Muhammad told his followers that the gates of Heaven would be open all the month and the gates of Hell (Jahannam) would be closed. The first day of the next month, Shawwal, is spent in celebration and is observed as the "Festival of Breaking Fast" or Eid al-Fitr.
The month of Ramadan traditionally begins with a new moon sighting, marking the start of the ninth month in the Islamic calendar. Many Muslims (except children, the sick and the elderly) abstain from food, drink, and certain other activities during daylight hours in Ramadan. This is considered as the holiest season in the Islamic year and commemorates the time when the Qu’ran (Islamic holy book) is said to have been revealed to the Prophet Muhammad.
Ramadan ends when the first crescent of the new moon is sighted again, marking the new lunar month’s start. Eid-al-Fitr is the Islamic holiday that marks the end of Ramadan.
Ramadan is also a time for many Muslims to donate to charity by participating in food drives for the poor, organizing a collection or charity event, and other voluntary activities. Muslims are encouraged to be charitable during Ramadan.
The Islamic calendar is a lunar calendar, and months begin when the first crescent of a new moon is sighted. Since the Islamic lunar calendar year is 11 to 12 days shorter than the solar year and contains no intercalation, Ramadan migrates throughout the seasons. The Islamic day starts after sunset.
Many Muslims insist on the local physical sighting of the moon to mark the beginning of Ramadan, but others use the calculated time of the new moon or the Saudi Arabian declaration to determine the start of the month. Since the new moon is not in the same state at the same time globally, the beginning and ending dates of Ramadan depend on what lunar sightings are received in each respective location. As a result, Ramadan dates vary in different countries, but usually only by a day. This is due to the cycle of the moon. The moon travels the same path all year round and when the moon is seen in the east, it is then seen traveling towards the west. All the countries around the world see the moon within a 24 hour period once spotted by one country in the east.
Each year, Ramadan begins about eleven days earlier than in the previous year. Astronomical projections that approximate the start of Ramadan are available. It takes about 33 years and five days for Ramadan to complete a twelve month move across the yearly calendar.