When Is Ramadan and When Does Fasting Start? In 2017, That's a Complex, Controversial Question

moon sighting ramadan Indonesia
An official looks through a telescope for a sighting of a new moon to start the Muslim fasting month of Ramadan at a religious boarding school in Jakarta, Indonesia, on May 26. Antara Foto/Rivan Awal Lingga/via Reuters

Ramadan is the holiest month in the Islamic calendar, and one that despite long days of fasting is highly anticipated by Muslims as an opportunity to get closer to God and their faith. However, many won't know when Ramadan starts until just a few hours before fasting begins.

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That's because the Islamic calendar is a lunar one, based on the crescents of the moon, and 11 days shorter than the Gregorian calendar. Thus, the dates for Ramadan change every year. While that is far from unique among religious holidays, the process of determining the start of the month of Ramadan is particularly complex—and controversial.

You might think that with modern astronomical tools, determining the start of a new moon would be straightforward enough. That is the case for some countries, such as Turkey and Iraq, and for Muslim communities in the United States and Europe, which base their start date on astronomical predictions. But others, such as Saudi Arabia, which is often referred to as the home of Islam, still choose to rely on the sighting of the first sliver of a new moon. Given that atmospheric conditions like cloud cover can play a part in the moon's visibility, and also that many Muslim-majority countries follow Saudi Arabia's lead, for tens of millions of Muslims, the time to start fasting often remains a mystery up until the night before.

The Judicial High Court of Saudi Arabia bases its declaration on the testimonies it receives from local moon sighters. Even within the country, the approach is not universally popular.

"Sometimes the moon was declared visible when it was astronomically impossible to declare it visible," Saraf al-Sufiani, head of the Horizons Society for Space Sciences in Jeddah, told Al Jazeera last year. "I don't see why we have to depend on people in the desert when astronomy can accurately tell the time of birth of the new moon with the accuracy of seconds, whether the crescent will be visible or not."

Many other countries choose not to accept Saudi Arabia's verdict in a dispute that goes right to the heart of the schism in Islam between Sunni and Shia. Notably, Shia-majority Iran often disagrees with its Sunni counterparts in Saudi Arabia about what exactly constitutes a new moon.

For 2017, astronomers have long since declared that the moon will first be visible around the world Friday evening. So countries that rely on such predictions, like Turkey and Iraq, had already stated that Saturday will be the first day of fasting, from dawn until dusk.

In Saudi Arabia, meanwhile, moon sighters were out Thursday evening but returned home without spotting a crescent. Attempted sightings in the Kingdom and other countries including the United Arab Emirates, were due to recommence Friday night.

A Muslim's location can determine more than just when Ramadan starts: It also has a major bearing on the length of each day's period of fasting from food, water and immoral acts. Indeed, the length of time will vary from just 11 hours and 32 minutes in Argentina to over 21 hours in Greenland.