How are prayer times calculated?
Where your country publishes a calendar, the app follows its authority's, and we tell you how we checked it. Where it doesn't, the app follows a known rule, which we name and explain.
This holds for Siam, Sujud and Falaq: the three apps calculate with the same engine, and give the same time at the same place.
Who decides the time?
Your country's religious authority. The app doesn't choose the time for it: it follows the calendar that authority publishes.
Everyone calculates the sun the same way, to within a few seconds. What changes from one country to another is how each time is defined: where dawn begins for Fajr, where night begins for Isha, one or two shadow lengths for Asr, a few minutes of precaution. From one choice to another, Fajr and Isha can move by 30 to 50 minutes, all year round.
Neither astronomy nor scholars impose a number: there is agreement on the sign, the dawn spreading across the horizon, not on an angle. The most common advice of fatwa bodies is to follow your country's authority, or your mosque. The app follows your country's authority.
Each method bears the name of the authority that publishes the calendar: the Ministry of Habous in Morocco, the Grande Mosquée de Paris in France, the Diyanet in Türkiye.
To know which country you are in, the app asks your phone. If it doesn't answer, offline for example, a world map built into the app takes over.
How do you know it's the right calendar?
We read it. We compare the calendar the authority publishes, minute by minute, with what the app calculates.
- We read the authority's own publication: its website, its PDF, its app. When we could only read a copy (a newspaper, a mirror site, mosques that reprint it), we note it. And when we could compare nothing, we say that too.
- A calendar is confirmed when the app matches it to within two minutes in the capital and in two other cities, far from it.
- When the authority publishes only one city, like Kabul, Baghdad or Tashkent, we say so: checked in a single city.
- The times we read stay in our tests: an update that drifted away from them would not get through unnoticed.
- Every month, a program re-reads the calendars that can be read automatically and compares them with the calculation. If the gap goes beyond what we know, we are alerted. This re-reading happens on our side: your phone never contacts these sites.
- The others, we re-read by hand, every year, in January.
- When a time moves in the app, we announce it and explain it in the release notes.
A calendar can change without warning: the Grande Mosquée de Paris changed its own in 2026, Malaysia in 2019. That's why we re-read.
And if my country doesn't publish a calendar?
The app then follows the Muslim World League's rule. It is a default rule, and we never pass it off as your country's calendar.
In several countries, Nigeria, Senegal, Sudan, Syria or China for example, we found no national calendar: the authorities announce the months and the feasts, and mosques take their times from the app or website of their choice. So there is no official time to follow.
The League's rule sets dawn when the sun is 18° below the horizon, and night at 17°. It bears the name of no country. Where a federation publishes its times in a country not yet on the list, in Nairobi, Seoul or São Paulo for example, it is within two minutes of this rule.
Your mosque, though, may have its own timetable. It can differ by a few minutes, and sometimes by much more at dawn: in Dakar or Bamako, some mosques set Fajr 20 to 40 minutes later. If you follow your mosque, choose in Settings, “Calculation method”, the one that comes closest.
Countries we haven't read enough yet get the same rule, in the meantime.
For the fast, which way does the app lean?
To the side of caution. When a choice has to be made, the app doesn't make you break your fast before the published time.
The rule of the minute. A calculation rarely lands exactly on a printed timetable. When two settings come equally close to it, we take the one that never makes you break the fast before the published time. The app's iftar therefore falls on the calendar's minute, or one to two minutes after, four at most in a few countries. For the other prayers, the app follows the calendar to within two minutes.
When no calculation matches the timetable. Some authorities publish times that no formula quite reproduces: observations, plateaus, fixed times. There, the app takes the setting that stays on the safe side of the timetable, every day of the year: the end of suhoor never after theirs, iftar and the prayers never before.
This choice has a cost, and we say so. In Ukraine, the app's end of suhoor falls 7 to 12 minutes before that of the Spiritual Administration of Muslims of Ukraine, and iftar up to 4 minutes after. In Russia, in summer, Isha falls up to 30 minutes after the Spiritual Administration's, in early August.
Why not put the timetable itself in the app? Because it would have to be replaced every year, in every app, and the app calculates everything on your phone, without downloading anything.
In Siam, the fast begins at Fajr, at dawn itself. Some calendars print an “imsak” a few minutes earlier, as a precaution: Siam doesn't add it.
The exceptions, one by one
- In Türkiye, the app applies the rule the Diyanet itself writes: sunset plus 7 minutes. Its timetables, though, drift from it with the seasons. In Istanbul, the app's iftar falls 1 to 2 minutes before the timetable on 143 of the 396 days read. We chose not to move the iftar of a whole country for those minutes.
- If you choose the Diyanet by hand in Sweden or Norway: 18 days a year in Stockholm and one in Oslo, the app's iftar falls one minute before the timetable.
- In the United Kingdom, in Birmingham: two days a year, at the turns of summer (18 May and 26 July in 2026), the app's end of suhoor falls 1 to 2 minutes after the Wifaqul Ulama's. Removing them would cost the whole country two minutes of suhoor, all year round.
- If you choose the Diyanet by hand in Ukraine: in Kharkiv, from April to August, the app's end of suhoor falls up to 2 minutes after the Diyanet's timetable.
Two authorities in my country: which one?
The one that works best, by default. The other is in the list of methods, under its own name, one tap away.
“Works best” means, in this order: a published calendar the app matches in several cities; then caution for the fast; then what the mosques practise.
| Country | By default | In the list |
|---|---|---|
| France | Grande Mosquée de Paris | Musulmans de France |
| United Kingdom | Wifaqul Ulama | London Unified Prayer Timetable |
| Germany | Diyanet, its European calendar | Muslim World League |
| South Africa | Jamiatul Ulama KwaZulu-Natal | Muslim Judicial Council (Cape Town) |
| Bahrain | The Bahraini calendar, the State's | Jafari method |
| Ukraine | Spiritual Administration of Muslims of Ukraine (DUMU) | DUMU “Umma” |
| Iraq | Diwan al-Waqf al-Sunni | Jafari method, for Najaf and Karbala |
| Netherlands, Belgium | The Dutch imams (VIN), the Executive of the Muslims of Belgium | Diyanet, for the Turkish mosques |
If your mosque follows the other one, choose it in Settings, “Calculation method”. Your choice is kept.
The app reads the country, not the region: in Cape Town as in London, it offers the country's calendar by default, and your city's is in the list.
And summer in the North? And days without night?
In summer, above 48° of latitude, dawn and night have to be estimated. The app takes your authority's summer rule when it publishes one; otherwise, a recognised rule, the same for all the apps.
In summer, in Paris, Brussels, London, Berlin and further north, the sun no longer goes far enough below the horizon: night never becomes fully dark, and dawn, in the sense of most calendars, never comes. It has to be estimated, and each authority has its own way. The same goes for the southern hemisphere.
Where your authority publishes its summer rule, it is theirs: the Grande Mosquée de Paris, the Executive of the Muslims of Belgium, the Dutch imams, the Wifaqul Ulama in the United Kingdom, the Spiritual Administration of Muslims of Kazakhstan, the Diyanet for its mosques in Europe. These rules differ a lot: in the United Kingdom, the Wifaqul Ulama places summer dawn in the middle of the night, and on 21 June in London the fast begins at 01:00 and lasts 20 hours and 28 minutes.
Elsewhere, the app applies the 1986 resolution of the Islamic Fiqh Council of the Muslim World League, adopted by the European Council for Fatwa and Research: dawn and night are estimated in proportion to what they are at the 45th parallel. Compared with official calendars, this rule most often makes the fast begin earlier and Isha fall later: the side of caution. Its downside: summer Isha often falls later than in the mosques.
Days without night, or without day. Beyond the polar circles, on some days, the sun doesn't set, doesn't rise, or stays too low for a shadow to exist. On those days, the app takes the times of the 45th parallel, as the same resolution provides: the same date, the same meridian, the same method. Your noon stays your noon.
These times are an estimate, not the sky's: on 21 June in Tromsø, Maghrib falls at 20:35, in broad daylight. For now, the apps don't say so on screen; this is where we explain it.
Where is the calculation done?
On your phone. Everything is calculated there: no account, no server, no calendar to download.
- Your location is used for the calculation; the app doesn't keep it from one opening to the next.
- No mosque timetable is downloaded or entered: the app calculates your authority's time, at the exact place where you are.
- Your lever is the “Calculation method” setting: you can choose another authority there, if your mosque follows another one. Your choice is kept from one update to the next; if that authority corrects its calendar, you get the correction.
- Asr follows the school of your country's calendar: one or two shadow lengths.
What doesn't the app promise?
Your mosque's exact minute. The app follows your country's authority; your mosque may have its own minutes.
- Far from the capital. In Bosnia, Albania, Bulgaria, Bangladesh and Belgium, the authority shifts the capital's timetable by a fixed number of minutes for each city. The app, for its part, calculates the sky above you. The gap ranges from a few minutes to a quarter of an hour, in summer.
- Your phone's clock. The times follow its clock: if it isn't on your country's legal time, after a time change it hasn't received yet for example, everything is shifted by as much.
- Near a border, offline. Without a network, the built-in map can get the country wrong a few kilometres from a border. The “Calculation method” setting then sets the right method.
- Near the date line. In Fiji or Tuvalu, one or two days a year are left without times.
- Altitude. Neither the app nor the authorities we read take it into account.
- Congregation times. The app gives the moment each prayer begins, not the time your mosque holds it in congregation.
- A calendar that changes without warning. We re-read, every month or every year; between two readings, a change can escape us for a while.
- A religious ruling. The app settles no question of fiqh: it follows your country's authority, and leaves the choice to you.
Does your country publish a calendar we haven't read? Send it to me: a link, a PDF or a photo is enough.
What counts is the authority's calendar, not a mosque's timetable: that's what we read to add a country.