Fajr time explained: how it's calculated, and why your apps and your mosque disagree

Two apps, one mosque timetable, three different Fajr times. Here is where the numbers come from — and which one to set your alarm by.

Updated October 3, 2026

What “Fajr” means: true dawn

Fajr starts at dawn — not at the first faint glow, but when the light spreads out along the horizon. The Qur'an describes this moment in the verse about the fast:

وَكُلُواْ وَٱشۡرَبُواْ حَتَّىٰ يَتَبَيَّنَ لَكُمُ ٱلۡخَيۡطُ ٱلۡأَبۡيَضُ مِنَ ٱلۡخَيۡطِ ٱلۡأَسۡوَدِ مِنَ ٱلۡفَجۡرِۖ

“…and eat and drink until the white thread (light) of dawn appears to you distinct from the black thread (darkness of night)…”

The verse sets the start of the fast, and the same dawn marks the start of the Fajr time. In Ṣaḥīḥ al-Bukhārī 621, the Prophet ﷺ explained that Bilāl's adhan at night did not mean dawn had started, and showed the difference with his fingers. One narrator passed the gesture on by stretching his two index fingers out to the right and left; the translator's note on sunnah.com explains that real dawn spreads left and right along the horizon, while light that appears high in the sky is not real dawn. Ṣaḥīḥ Muslim 1094a makes the same point: the whiteness counts once it spreads. The chapter heading there calls this the second or “true dawn”, the one that marks the start of the fast and of the time for the Subḥ (Fajr) prayer, and calls the first glow the “false dawn”.

The time ends at sunrise. The Prophet ﷺ said:

“When you pray Fajr, its time is until the first part of the sun appears.”

How an app turns dawn into a clock time

Few of us watch the horizon every morning, so timetables calculate dawn instead. The idea is simple: the sky starts to brighten when the sun, still below the horizon, rises to a certain angle beneath it. Astronomers call the moment the centre of the sun reaches 18° below the horizon in the morning “astronomical dawn”.

Every calculation method picks its own angle. A larger angle means the sun is deeper below the horizon, so Fajr comes earlier. A smaller angle gives a later Fajr. That single number explains most of the differences you see between apps.

The calculation methods and their angles

These are eight widely used methods. The values come from the source code of the open-source adhan library for calculating prayer times, version 2.0.0+1.

Two things stand out. First, four methods — MWL, Karachi, Turkey and Kuwait — share the same 18° Fajr angle, so they give the same Fajr time; they differ in ʿIshāʾ or sunrise. Second, the full range runs from 15° to 19.5°. The library also includes Singapore (20°), Qatar (18°), Tehran (17.7°) and the Moonsighting Committee method (18° with seasonal adjustments).

One city, one day, eight answers

Here is Fajr in London (51.5074° N, 0.1278° W) on three dates in 2026, calculated with the adhan library, version 2.0.0+1. Times are UK local time (BST in October and June, GMT in December). The high-latitude rule is “twilight angle”, except for Umm al-Qurā: the library's twilight-angle rule needs an ʿIshāʾ angle, which Umm al-Qurā does not have, so here it uses “last seventh of the night”. Both rules are explained below.

On an ordinary October morning, the methods are 31 minutes apart. Umm al-Qurā looks odd: its angle is larger than MWL's, yet its Fajr is later in October and June. That is the last-seventh rule used for it here — it never lets Fajr fall earlier than the start of the last seventh of the night, and in London that limit is later than the 18.5° time.

High latitudes: the UK, Canada and Northern Europe

In London around midsummer, the sun never sinks 18° below the horizon — at its lowest it is only about 15° below. So an 18° Fajr simply does not happen, and the plain calculation has no answer. Around midsummer this happens anywhere north of about 48.5° latitude — Paris, London, Berlin, Edmonton and Stockholm included.

A high-latitude rule fills the gap by setting the earliest allowed Fajr as a share of the night (sunset to sunrise). The adhan library has three:

• Middle of the night: Fajr is never earlier than the midpoint of the night.
• Last seventh of the night: Fajr is never earlier than the start of the last seventh of the night.
• Twilight angle: the share of the night is the Fajr angle divided by 60 — for 18°, that is 18/60, the last 30% of the night.

The choice matters. In London on 21 June 2026, the MWL method gives Fajr at 01:02 with “middle of the night”, 02:31 with “twilight angle” and 03:40 with “last seventh”. In December all three rules give the same 05:59, because the normal calculation works again.

Beyond the Arctic Circle, none of these rules help: on some days the sun does not set or does not rise, so there is no night to divide. Calculation libraries offer fallbacks, such as borrowing the times of the nearest day that can be calculated. If you live that far north, your local mosque or Islamic centre is the place to ask.

Why your apps and your mosque disagree

• Different methods. One app uses 15°, another 18°, and your mosque perhaps 19.5° — that alone is half an hour.
• Different high-latitude rules. In summer at higher latitudes, the rule can matter more than the method, as the June column shows.
• Different locations. An app uses your phone's position or the city you entered; a mosque timetable is made for its own neighbourhood. Every degree of longitude east or west moves the times by about four minutes.
• Start time vs. congregation time. Many mosque timetables list both the start of Fajr and the iqāmah, when the congregation prays. Compare the start times, not the iqāmah.
• Local timetables. Some mosques follow a timetable set by their own scholars or a local committee, and it may not match any of the standard angles.

Which time should you follow?

Match your local mosque. Look at its timetable for the start of Fajr, then pick the method in your app that comes closest — compare a few days, and in summer check the high-latitude rule too. This guide does not judge which method is religiously correct; if you are unsure, ask your imam or a scholar you trust.

What time should you wake up?

Fajr runs from true dawn to sunrise — on 3 October 2026 in London, about an hour and fifty minutes with the MWL method. Set your alarm a little before the start time your mosque gives, with enough time for wuḍūʾ and getting ready, and plan back from the iqāmah if you pray in congregation. Because Fajr moves every day — in London by more than three hours on the clock between June and December — a fixed alarm time drifts away from it. Fajr Up re-times its alarm every night from the method you choose and lets you set it from 60 minutes before to 30 minutes after Fajr (how it works). For the getting-up part, see how to wake up for Fajr.

Frequently asked questions

Keep reading

• How to wake up for Fajr: a practical guide for people who keep sleeping through it
• Why your Fajr alarm didn't ring on iPhone — and how to fix it tonight
• Dua to wake up for Fajr: what to say when you wake — and how to ask for help the night before

Sources

1. Qur'an 2:187, translation Hilali-Khan – quranenc.com
2. Ṣaḥīḥ al-Bukhārī 621 – sunnah.com
3. Ṣaḥīḥ Muslim 1094a – sunnah.com
4. Ṣaḥīḥ Muslim 612a – sunnah.com
5. Astronomical twilight – timeanddate.com
6. adhan (Dart), calculation_method.dart – angles of each method
7. adhan (Dart), high_latitude_rule.dart – the three high-latitude rules
8. adhan-js, Calculation Parameters Guide (METHODS.md)

Sources checked on 3 October 2026 at quranenc.com, sunnah.com and timeanddate.com. Angles and example times checked against the source code of the adhan package, version 2.0.0+1.

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