Today, Muslims around the world celebrate Eid al-Fitr to mark the end of the holy month of Ramadan. However, different countries – and, as is the case in Lebanon, different communities within a country – do not celebrate the feast on the same day. Various schools of thought and methods for determining exactly when the month of Shawwal starts – signifying the end of Ramadan – abound within both the Sunni and Shia sects.

To the moon

The Islamic calendar is based on lunar months. Instead of the regular 30 and 31-day months of the heliocentric (sun based) Gregorian calendar, lunar months are 29 or 30 days, depending on the moon cycle. While moon cycles are now perfectly predictable to the second, there is much debate surrounding the exact coordination between moon and sunsets.

The Quran says one begins and ends Ramadan’s fasting the day after seeing the sign of a new month’s beginning (the waxing crescent moon, often just a sliver in the sky visible for only a few hours, which follows the moonless night of the new moon). Some Sunni and Shia communities still depend entirely on actually seeing this fraction of the celestial orb with their own eyes to call both the beginning and end of Ramadan. In Lebanon, the country’s Higher Islamic Council, for example, waits for Iraq’s Sayyed Ali al-Sistani to declare a full moon, while political party Hezbollah takes its lunar cue from Iran’s Ayatollah Ali Khamenai, who also depends on a sighting, although some members of Hezbollah follow Sistani.

By the numbers

Elsewhere in Lebanon, the respected Shia cleric, Sayyad Muhammad Hussein Fadlallah, depends entirely on scientific calculations and could presumably announce the beginning and end of Ramadan for hundreds of years to come.

There is one complication in this approach, one that manifested itself this year. The waxing crescent moon first shone on Lebanon on Monday – during the day. Since days on a lunar calendar go from sundown to sundown, many think that the moon’s appearance during the day does not count.

So even though science says the waxing crescent moon was hidden somewhere in the bright, cloud-filled skies over Lebanon on Monday, many clerics will wait until Tuesday, when the sliver appears post-sundown, to announce Eid al Fitr’s start as the following day, even if they don’t depend on actually seeing it.

Fadlallah, is understood to disagree, believing that if the waxing crescent moon appears in the night sky over any country that shares some nighttime hours with Lebanon, the Eid al Fitr holiday can begin the next day. He can also extrapolate: on September 25, the moon was sighted over the south-western portion of South America prompting Fadlallah to officially announce the celebration’s start as Tuesday, September 30.

Calls for consistency

This range of opinion and practice is possible because there is not one, authoritative head of the Islamic community.  Several groups exist that call for adopting one system for deciding when Eid al Fitr should be celebrated to unite believers. Calls by these organizations, such as the Islamic Crescent Observation Project founded in 1998, have gone unheeded, even though clerics interviewed for this article dismissed suggestions that political considerations underlie different views on when the holiday starts.