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The holy month of Ramadan celebrated by over a billion Muslims worldwide commences Wednesday night, with a month-long observation full of fasting, charity and community services. Here are some key facts about the sacred month.

 When Does It Begin?

The first of Ramadan is likely to fall on Wednesday evening March 22 with fasting to begin Thursday morning — all depending on if the moon is sighted. The month runs by the Islamic Lunar calendar which begins the at sighting of the crescent moon.

Why is the month sacred?

Muslims believe that the Quran, the sacred text, was first revealed to the last Prophet Muhammad (Peace Be Upon Him) over 1,400 years ago, Al Jazeera reports.

What do Muslims do in Ramadan?

Muslims fast from dawn to sunset, abstain from food, water and actions that pollute the soul. It is also a time where people prioritize prayer, spiritual reflection, charity and other acts of goodness.

Fasting is known as one of the five pillars of Islam, the other four being declaration of faith, prayers, charity and the Hajj pilgrimage.

According to Al Jazeera, many in Muslim-majority countries, working hours are cut and many restaurants are closed during fasting hours.

What marks the end of Ramadan?

Ramadan is observed for roughly an entire month, ending when the new moon is sighted which is estimated to fall on April 21, marking the celebration, Eid.