Ramadan begins with the crescent moon. Here’s why the official start time can still vary around the world

The Islamic calendar does not follow the sun; rather, it follows the lunar cycle and the phases of the moon.

(CNN) — You might already know that roughly a quarter of the world’s population is expected to head into Ramadan this weekend, the Islamic holy month perhaps best known for its followers’ dawn-to-sunset abstinence of food and liquids.

What you might not realize if you’re not a follower: Muslims tentatively know when it’s coming up, but they may get a notice of mere hours of when Ramadan officially starts.

Further, it’s not uniformly observed around the world — the start date can vary country to country and can even be different mosque to mosque in the same city. But what unites all Muslims is the observance of the new crescent moon in the ninth month of the Islamic calendar.

For instance, in Saudi Arabia, where Islam was first established by the prophet Mohammed in the 7th century, that new moon is tentatively expected to be visible on the evening of February 28, and thus Ramadan would begin on Saturday, March 1.

Thousands of miles to the east of Saudi Arabia, in Indonesia, the angles of lunar visibility are different, and they’re expecting to begin on Sunday, March 2.

In 2024, Saudi Arabia and its smaller Arabian Peninsula neighbor Oman started one day apart.

Why does that happen that way? Well, it’s frankly a complicated mix of considerations, said Professor Scott Kugle of the Department of Middle Eastern and South Asian Studies at Emory University in Atlanta and author of “Hajj to the Heart: Sufi Journeys across the Indian Ocean,” the most recent of his scholarly books.

They include among others:

· Astronomical sightings and how they’re made

· Global geography and time zones

· Various traditions among different groups of Muslims

· Even current weather conditions

A key point that is “really important, I think, for Westerners to understand is that there really is no central authority among Muslims. It’s all very local, depends on what mosque you go to, what your family network is,” Kugle said in a phone interview.

That’s why you get such national and even citywide variations in the start time, Kugle says. And given the different interpretations, it’s possible for the actual start date to fall one day before or one day after the tentative date.

That’s “why people have a lot of excitement in the week building up because they’re kind of shopping, preparing,” he said. “There’s a great deal of uncertainty: ‘What day is it going to begin?’ ”

And that answer lies in the sighting of a particular phase of the moon.

It’s all about the crescent moon

The Islamic calendar does not follow the sun; rather, it follows the lunar cycle and the phases of the moon.

Probably the best-known phase is the “full moon,” when the largest surface of the moon is brightly illuminated from Earth’s perspective. The invisible phase of the moon, when the illuminated side of it is facing the sun and the night side is facing Earth, is the “new moon.”

Ramadan commences when a small sliver of the moon, known in astronomical terms as the “waxing crescent,” emerges and becomes visible. And that’s true across the Islamic world.

But from there, things start to get complicated and decentralize quickly, Kugle said. First off, there are two ways to determine a crescent moon sighting.

“One is by seeing it, and one is by calculating it astronomically,” Kugle said. “And the traditional, old-fashioned way, of course, is to see it.

“It’s not that everyone has to see it, but people in charge have to see it. So some communities will have appointed a moon-sighting committee, and they go up on a high position or on a beach where there’s an unobstructed view of the horizon and they wait to see if they can see the new crescent moon, and it usually appears for a short time after sunset.”

And if they don’t see it? “Then they say, ‘OK, the month has not started.’ ”

Naked-eyed observations can bring in other complicating factors, such as local cloud cover. A crescent might be spotted in one place, but not in another place nearby.

Other places rely on astronomical calculations, with Turkey being an example of that.

“Islamic scholars have stated that both ways of moon sighting are permissible, and that people should act according to their local situations,” according to Turkish Radio and Television World.

Other factors in Ramadan timing

The variables in crescent moon sightings aren’t the only things in play.

“There is no central authority for Muslims, and there are some pretty basic divisions between Muslims, like in Christianity [with] Catholics and Protestants and Orthodox,” Kugle said.

“So, in the Muslim world, too, you’ve got Sunnis and you’ve got Shi’i (Shia) and you’ve got others. And those groups may make their own determination of when the moon gets sighted. And it might be on different days, right?”

Even human emotions can be involved.

“It’s kind of like pride to not start on the same day as the other group. … Even in a majority Sunni country, a Shi’i (Shia) minority might start on a different day,” Kugle said.

What people are doing half a world away or next door can factor in.

“It’s all very local, depends on what mosque you go to, what your family network is. People in North America who have family back in India, let’s say, or Pakistan may start fasting in North America when their families back in Pakistan or India start fasting.”

Want to consider yet another variable? Stop and think about the vastness of the planet, all 24 time zones — and the fact that Muslims are spread around the world.

“The moon’s going to be in a different situation when the sun sets in Indonesia compared to when it sets in Saudi Arabia compared to when it sets in Chicago,” he said.

The Islamic calendar

If you’re thinking, “Hey, I recall that Ramadan started later than this last year,” you’d be right.

That’s because the aforementioned Islamic calendar follows the lunar cycle with months of either 30 or 29 days. The result: a year consisting of 354 or 355 days.

Now compare that with the Gregorian calendar, started in 1582 and in use around much of the world. And it is based on a solar cycle consisting of 365 days (or 366 in a leap year).

So when you overlay annual Ramadan occurrences over the Gregorian calendar, it gives the appearance of falling further back each year, some 10 to 12 days each time. In fact, it takes Ramadan 33 years to circle the entire Gregorian calendar and all four seasons.

Changes in latitudes

While latitude (the distance north or south of the equator) does not directly affect when Ramadan starts, it has a whole lot of impact on what the Ramadan fasting experience will be like for adherents.

Muslims at or near the equator have rather uniform fasting experiences each year throughout the seasons, with roughly 12 hours of light and fasting and 12 hours of darkness to break the fast. But it can get quite different as you get closer to the North Pole or South Pole, which have extreme swings between daylight and darkness during summers and winters.

“Atlanta is pretty good, you know; the days and nights don’t change radically,” said Kugle, who follows Sufism, a branch of Islam that emphasizes spirituality. “I’ve fasted Ramadan living in Amsterdam before, and I have friends who fast Ramadan in Helsinki in Finland, and that’s pretty hard in the summer. Those are long days.

“In fact, if you get really far up in Scandinavia, some Muslims have said that you can’t follow the sun because that’s too much of a hardship, and so they just say whatever happens in Mecca … we’ll set the time for that.”

A shared spiritual reawakening

Despite all the complications of when it starts and how long a daily fast might last, “Ramadan is one of the things that is shared by all Muslims no matter what their sect or their orientation or their style,” Kugle said.

“There are special Ramadan foods in every culture that only come during this period, and people really look forward to it,” Kugle said while talking about the communal spirit in breaking the fast together.

“It really is an amazing time where people come together. … It’s something that turns your routine upside down … because we normally get up, we have breakfast, we have coffee, we think what are we having for lunch, we have lunch meetings, we meet friends for dinner. Like, none of that happens. It’s all turned upside down.”

“It’s a great time to shake your routines and to question … ‘Where am I putting my energy?’ ”

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