According to Islam, the Quran was sent down to the lowest heaven during this month, thus being prepared for gradual revelation by Jibra'il to Muhammad.

[1] The first three days of the next month, Shawwal, are spent in celebration and are observed as the "Festival of Breaking Fast" or Eid al-Fitr.

The Islamic calendar is a lunar one, where each month begins when the first crescent of a new moon is sighted.

The estimated start and end dates for Ramadan, based on the Umm al-Qura calendar of Saudi Arabia, are:[2] 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.