Every year the same thing happens. One country announces that Ramadan begins on Tuesday, another on Wednesday, and two mosques a few miles apart follow different announcements. Families split across borders fast on different days, and Eid — which ought to be the most collective day of the year — lands on two dates.
It is worth knowing that this is not confusion, and not a failure of astronomy. The moon's position is known to the second. What differs is the question being asked about it.
The month begins with a sighting, not a calculation
The Islamic month is lunar, and the classical rule is that it begins when the new crescent — the hilal — is actually seen. The hadith is explicit about the method: fast when you see it, and break the fast when you see it, and if it is obscured, complete thirty days. That instruction is about observation, not arithmetic.
This matters because astronomical new moon and visible crescent are different events, usually by a day or more. At the astronomical new moon the moon sits between the earth and the sun and is not visible at all. It becomes visible only once it has moved far enough away, is high enough above the horizon at sunset, and the sky is dark enough for a very thin arc to register against it. Whether that threshold is crossed on a given evening depends on where you are standing, what the weather is doing, and how sharp the observer's eyes are.
So a crescent genuinely visible in Morocco can be genuinely invisible in Indonesia on the same evening, and both reports are correct.
Four positions, all reasoned
The differences between countries come from four defensible answers to what should be done with that fact.
- Local sighting. The month begins when the crescent is seen in your own region. This keeps closest to the literal instruction, and it is why neighbouring countries can legitimately differ — they are separate localities with separate skies.
- Global sighting. A confirmed sighting anywhere in the Muslim world begins the month everywhere. This treats the community as one body rather than a set of regions, and it is why some communities follow an announcement made thousands of miles away.
- Calculation. The month begins when astronomical criteria for visibility are met, whether or not anyone looked. Proponents argue that the instruction to sight was practical guidance for a time without reliable astronomy, and that certainty is now available. It also allows a calendar to be printed a year ahead, which matters for anyone who has to book leave.
- Following a specific authority. Many communities simply follow the announcement of a particular body — a national religious authority, or the Saudi announcement — as a matter of unity rather than of independent judgement.
Why calculation does not settle it
It is tempting to assume that calculation is the modern, obviously correct answer. The difficulty is that there is no single calculated criterion either. Different bodies use different visibility thresholds — minimum altitude of the moon at sunset, minimum angular distance from the sun, minimum time since conjunction — and those thresholds themselves produce different answers on the marginal evenings, which are exactly the evenings anyone argues about.
The disagreement, in other words, does not get resolved by better instruments. It is a question about what the instruction requires, and that is a scholarly question rather than a technical one.
What to do about it
The practical answer is straightforward and has been for a long time: follow your local mosque or national authority, and do not treat someone following a different one as having got it wrong. Both positions have serious scholarly backing, and the point of the month is not won by being on the earlier date.
For planning purposes, treat printed dates as estimates. The Ramadan 2027 page on this site gives the expected start based on astronomical calculation, and says plainly that the confirmed date depends on the sighting and the authority you follow. Any site that gives you a date for next Ramadan with no such caveat is overstating what is knowable.
One more practical note for families split across countries: fasting is tied to where you are, not where you are from. If you travel mid-Ramadan, you follow the local timetable when you arrive — which is also why the prayer times here recalculate the moment you change the city.
Common questions
- Why does Ramadan start on different days in different countries?
- Because communities follow different methods for beginning the month: local crescent sighting, a global sighting accepted from anywhere, astronomical calculation, or the announcement of a particular authority. All four have scholarly backing, and on marginal evenings they produce different dates.
- Is it wrong to start Ramadan on a calculated date?
- It is a position held by recognised scholars, not an error, though others hold that actual sighting is required. There is also no single calculated answer — different bodies use different visibility thresholds and disagree on exactly the borderline evenings.
- Which day should I follow if my family is in another country?
- The usual guidance is to follow the community where you are. Fasting tracks the place you are in rather than your country of origin, which is also why you switch to the local timetable if you travel mid-month.
- Can Eid be on different days too?
- Yes, for the same reason and by the same mechanism — Eid al-Fitr begins the month of Shawwal, so it depends on the sighting of the same crescent and on whichever method a community follows.