Calculation vs Local Sighting: Why Muslims Start Ramadan on Different Days

Twice a year the same conversation happens in families and mosques around the world: “Has Ramadan started?” “Is Eid tomorrow or the day after?” Different countries — and sometimes different mosques in the same city — announce different days. It can look like confusion. In reality it reflects a small number of well-defined positions, each held in good faith and each with its own reasoning.

This guide sets out those positions as fairly as possible. It is not a ruling; for that, follow a scholar or authority you trust.

The common ground

All Muslims agree on these points:

• Islamic months are lunar and begin with the new crescent.
• A month has 29 or 30 days.
• If the crescent is not seen on the 29th evening, the month is completed to 30 days.
• The goal is to start and end the fast at the right time, and to celebrate Eid together as a community.

The disagreement is about whose sighting counts, and whether calculation can replace or supplement sighting.

Position 1: local sighting

What it says: each region starts the month according to the crescent seen in that region (or in places sharing the same horizon).

The main evidence: the hadith of Kurayb, recorded in Sahih Muslim (1087). Kurayb was in Syria when the crescent of Ramadan was seen there on a Friday night; when he returned to Madinah, Ibn Abbas said they had seen it on the Saturday night and would continue fasting until they completed thirty days or saw the crescent, adding, “This is how the Messenger of Allah commanded us.” Many scholars understood this to mean that each region follows its own sighting.

Who follows it: it is the traditional position of the Shafi’i school and is followed, with variations, in countries such as Pakistan, Bangladesh, India and Morocco, and by many communities elsewhere.

Practical result: countries far to the east of the Middle East often begin months a day after Saudi Arabia, because the crescent is harder to see there on the same evening.

Position 2: global (unified) sighting

What it says: a sighting anywhere in the world — or at least anywhere it is reliably reported — obliges all Muslims to start the month.

The main evidence: the general wording of “Fast when you see it”, addressed to the whole community, and the view that differences in horizon (ikhtilaf al-matali’) should not divide the Muslim community. This is the majority position among Hanafi, Maliki and Hanbali scholars in classical works, although many of them also accepted local practice where news could not travel in time.

Who follows it: many communities in Europe and elsewhere apply it in practice by accepting sightings from other countries.

Practical result: the whole community starts on the earliest reliable sighting, which often means the same day as the Middle East or earlier.

Position 3: following Saudi Arabia

What it says: follow the announcement of the Saudi Supreme Court, especially for Ramadan and the Eids, either because of the importance of Makkah or because it is the most visible reference for a global community.

Reasoning: for Hajj and the Day of Arafah, everyone follows Saudi Arabia’s determination of Dhul-Hijjah, since the rites take place there. Some extend this to all months for unity and simplicity.

Who follows it: most Gulf states and a significant number of communities in Europe, Africa and elsewhere.

Practical result: dates match Saudi Arabia, which usually but not always matches the Umm al-Qura calendar.

Position 4: astronomical calculation

What it says: since the purpose of sighting is to know when the month begins, and astronomy can now determine this precisely, a pre-calculated calendar may be used.

The main evidence: the hadith “We are an unlettered nation; we do not write or calculate. The month is like this and this” (Sahih al-Bukhari 1913) is read as describing the circumstances of the time rather than forbidding calculation. Some point to the hadith “if it is obscured, then estimate for it (faqduru lahu)” (Sahih al-Bukhari 1906) as allowing estimation.

Who follows it: the Fiqh Council of North America adopted a calculation-based approach in 2006; Turkey’s Diyanet publishes a calculated calendar, and the 2016 International Hijri Calendar Unity Congress in Istanbul proposed a single calculated calendar for the world. Several Muslim organisations in Indonesia also use calculation (hisab).

Practical result: dates are known years in advance; they may differ by a day from local or Saudi sighting.

A widely held middle ground: calculation to reject, sighting to accept

Many scholars and committees who require sighting still use astronomy in one important way: to reject claims that are astronomically impossible. If the moon had already set before the sun on the evening in question, or conjunction had not yet occurred, a reported sighting cannot be accepted, however sincere the witness.

This position — sometimes summarised as “calculation for negation, sighting for affirmation” — is held by many contemporary jurists and is applied by several national committees.

Why calculated calendars still differ from each other

Even calculation-based calendars can disagree, because they choose different criteria:

• Conjunction before sunset (and moonset after sunset) at Makkah — the Umm al-Qura approach.
• Visibility somewhere on Earth before midnight GMT — used in some global calendar proposals.
• Visibility in a particular region — used by some national calendars.

So “using calculation” is not one method but a family of methods.

Which should you follow?

The overwhelming advice of scholars is practical: follow the recognised authority of the community you live in. The Prophet ﷺ said: “The fast is the day you all fast, and the breaking of the fast is the day you all break it, and the sacrifice is the day you all sacrifice” (Sunan al-Tirmidhi 697). Fasting and celebrating with your community is itself a value.

If your community has more than one mosque following different methods, choose one with good reason and stay consistent for the whole month — start and end Ramadan with the same authority.

The arguments people make — and the replies

Discussions about method often circle around a few recurring arguments. Here they are, with the replies typically given by the other side.

“Calculation gives certainty; sighting gives confusion.” Reply: certainty about the astronomy is not the same as certainty about the legal criterion. The hadith tie the month to seeing, and many scholars hold that the act of sighting is itself what the law requires, not merely a means to an end.

“Local sighting divides the community.” Reply: the community that matters for fasting together is primarily the local one — the people you pray and break the fast with. A city in which every mosque follows the same local authority is united, even if another country is a day apart.

“Following Saudi Arabia is simplest.” Reply: it is simple, and many scholars accept it, especially where no reliable local authority exists. Others note that Saudi Arabia’s own announcements are based on sighting within Saudi Arabia, which is itself a form of local sighting.

“Global sighting is the majority view.” Reply: it was the view of many classical jurists, but they lived when news could not cross continents in a night. Applying it today raises new questions — for example, whether a sighting in the Americas should oblige people in Asia who have already passed the relevant evening.

Each position has scholars of standing behind it. The arguments are worth understanding, not to win a debate, but to respect the choices other communities make.

How to plan when the date is uncertain

• Use the calculated date for planning. The Umm al-Qura calendar gives expected dates months in advance — Ramadan 1448 on 8 February 2027, Eid al-Fitr on 9 March 2027.
• Plan for one day either way. Book leave or travel with a day’s flexibility.
• Check your country’s page. Our Hijri date by country pages show the calculated date in each country’s time zone and note where local sighting usually runs a day later.

A note on tolerance

These differences are among the oldest in Islamic law, and great scholars have held every one of these positions. Disagreement over method is not disagreement over faith. When neighbours celebrate Eid a day apart, both are trying to do the same thing: to follow the moon as they understand the Prophet ﷺ taught.