How prayer times are calculated, and why apps disagree

Before there were apps, there was the sky. Every Muslim prayer time is tied to something you could once see with your own eyes: the first light along the horizon, the sun at its height, a shadow growing long, the sun slipping away, the last glow fading. The signs were set by God; our clocks only try to keep up with them.

So why does your phone say Fajr is at 5:12 when the mosque timetable on the fridge says 5:41? The signs are fixed, but turning them into minutes takes a few judgement calls. This guide walks through where the times come from in the Qur’an and Sunnah, what each one looks like in the sky, why calculation methods differ, and how to find the one your community uses.

The times come from revelation, not convenience

The Qur’an tells believers that prayer has fixed times, and describes them by the sky, not the clock:

Other verses sketch the shape of the day. One commands prayer “at the decline of the sun until the darkness of the night, and the recitation at dawn” (Sūrat al-Isrāʾ, 17:78). Many commentators read this as the sun passing its height (Dhuhr and Asr), the darkness of night (Maghrib and Isha) and dawn (Fajr). Another verse says:

The Sunnah fills in the detail. The angel Jibrīl (peace be upon him) led the Prophet ﷺ in each prayer on two days at the Kaʿbah, first at the start of each time and then near its end, and said: “Muḥammad, this is the time of the prophets before you, and the time is between these two times” (Sunan Abī Dāwūd 393 and Jāmiʿ at-Tirmidhī 149; graded ḥasan ṣaḥīḥ by al-Albānī). The Prophet ﷺ also summed it up in words: “The time of Dhuhr is when the sun has passed the meridian, and a man’s shadow is the same as his height, as long as Asr has not come. The time of Asr lasts as long as the sun has not turned pale. The time of Maghrib lasts as long as the twilight has not disappeared. The time of Isha lasts until the middle of the night. And the time of Fajr is from the appearance of dawn, as long as the sun has not risen” (Ṣaḥīḥ Muslim 612).

Each prayer has a window, not a single moment. A timetable shows when each window opens, and that is the number every app tries to compute.

What each time means in the sky

Fajr: true dawn. The Prophet ﷺ distinguished two kinds of early light. A thin vertical column of brightness, the “false dawn”, does not mark Fajr; the true dawn is the whiteness that spreads horizontally along the horizon (Ṣaḥīḥ Muslim 1094). The Qur’an uses the same image for the start of the fast: “until the white thread of dawn becomes distinct to you from the black thread” (Qur’an 2:187). Calculations describe dawn by how far the sun is below the horizon, and methods put true dawn between 15° and 20° below it. Fajr’s window closes at sunrise.

Dhuhr: just after noon. At solar noon the sun is at its highest and shadows are shortest. The moment it begins to decline, called zawāl (the sun passing the meridian), Dhuhr begins. It depends only on your longitude, your time zone and the date, so it is the easiest time to calculate. Many methods add a minute or more after true noon as a precaution.

Asr: when shadows grow long. Asr is defined by shadow length. Picture a stick in the ground. The Shāfiʿī, Mālikī and Ḥanbalī schools begin Asr when its shadow equals its length, plus the shadow it already had at noon. The Ḥanafī school begins it when the shadow reaches twice the length, plus the noon shadow. Both views have evidence behind them and centuries of practice. Depending on latitude and season, the gap between them runs from about half an hour to well over an hour, so two mosques in the same city can call Asr far apart.

Maghrib: sunset. Describing when the fasting person breaks the fast, the Prophet ﷺ put it simply: “When night falls from this side and the day vanishes from this side and the sun sets” (Ṣaḥīḥ al-Bukhārī 1954). In calculations it is the moment the sun’s upper edge disappears, allowing for the way the atmosphere bends light, so the astronomical sunset is the same in every method; any difference comes from a few precautionary minutes some authorities add.

Isha: nightfall. Isha begins when the twilight, ash-shafaq, has gone. Most scholars, including Abū Ḥanīfah’s two leading students, understood it as the red glow after sunset; Abū Ḥanīfah held it is the white glow that lingers after the red, which comes later. Methods express nightfall as an angle, usually 14° to 18°, or as a fixed number of minutes after Maghrib.

Ṣaḥīḥ Muslim 612 gives the middle of the night as Isha’s end. Scholars differ on the time after that: many hold that Isha prayed before dawn is still valid, though delaying it without reason is disliked, while others are stricter. If this affects you, ask a scholar you trust.

Why your app and your mosque disagree

Dhuhr and Maghrib are almost pure geometry, and Asr depends on a school you choose once. The real disagreements are at Fajr and Isha, because twilight brightens and fades gradually, with no sharp line in the sky. Scholarly and official bodies looked at the same signs and, drawing on their own observations and judgement, settled on different angles.

Each set of choices is a calculation method. Some widely used ones, with their Fajr and Isha settings:

• Muslim World League — 18° / 17°. A common worldwide default.
• Egyptian General Authority — 19.5° / 17.5°. Used in Egypt and much of the Levant.
• Karachi (University of Islamic Sciences) — 18° / 18°. Common in Pakistan and India.
• Umm al-Qura (Makkah) — 18.5° for Fajr; Isha a fixed 90 minutes after Maghrib, and 120 minutes during Ramadan.
• ISNA (North America) — 15° / 15°. Gives a later Fajr and an earlier Isha.
• Diyanet (Turkey) — 18° / 17°, plus precautionary margins of a few minutes (sunrise earlier; Dhuhr, Asr and Maghrib later).

Switching from a 15° method to a 19.5° one moves Fajr earlier by 20 minutes or more at mid-latitudes, and by far more in a northern summer. That is usually the whole mystery behind “my app is wrong”. Neither number is a mistake; they are two careful answers to “when does true dawn begin?”

One rule changes with the month. During Ramadan, Saudi Arabia’s official Umm al-Qura timetable moves Isha from 90 to 120 minutes after Maghrib. If you follow that method, expect Isha half an hour later until Eid. (How the month itself is fixed is covered in our Ramadan 1448 guide.)

The sun keeps perfect time. Our methods are careful, humble attempts to read it.

High latitudes: when the night never gets dark

For the sun to sink 18° below the horizon at midnight in late June, you need to be south of about 48.5° north. London sits at 51.5°, where on the shortest nights the sun dips only about 15° below the horizon, so an 18° method never finds true dawn or full nightfall. Further north, twilight lasts all night for weeks.

The Sunnah gives a principle for unusual days. When the Prophet ﷺ described a time when a day would be as long as a year, the Companions asked whether one day’s prayers would suffice. He said: “No, but estimate its due measure” (Ṣaḥīḥ Muslim 2937). Scholars took from this that where the usual signs are missing, the times are estimated rather than abandoned.

How to estimate is where opinions differ. Common approaches take Fajr and Isha from a fraction of the night (such as one-seventh), from the nearest latitude where the signs still appear, or from the last day they appeared. Mosques this far north publish the approach they follow, and their summer timetable is your safest guide.

How to match your local mosque in five minutes

Praying with your community is easier when your phone agrees with the mosque:

1. Get the mosque’s timetable for this month. Read the start (adhān) times, not the congregation (iqāmah) times, which are usually later.
2. Check Dhuhr and Maghrib first. These barely depend on the method. If they are off by more than a few minutes, check your location and time zone before anything else (a Diyanet-style margin can account for five to seven).
3. Compare Fajr and Isha across two or three methods in your app. The one that matches within a minute or two is almost certainly the one the mosque uses. If none match, ask the mosque; some publish their own adjusted timetable.
4. Set your Asr school to match the mosque, or the school you follow yourself.
5. Re-check in summer, and when you travel. Some mosques switch rules for high-latitude summers, and methods follow regions, so a match at home in March may not hold in June or abroad.

Awwab calculates times on your phone, offline, with eleven methods including all of the above, and lets you pick your Asr school. If your phone tends to pull you away at prayer time, it can also pause the apps you choose until you’ve prayed. More on the features page, or in our guide to keeping your five prayers when your phone fights back. If a window does slip past, see making up missed prayers.

If you enjoy the reasoning behind everyday worship, finding the Qibla applies the same sky-and-geometry thinking to direction, the Knowledge Hub has longer guides, and the Knowledge game puts a source behind every answer (see how we check them).

Frequently asked questions