Why prayer time apps disagree with each other (and with your mosque)

You install a prayer times app. Your friend has a different one. Same city, and the Fajr times differ by eleven minutes. One of them must be wrong.

Neither is. This article explains why, because understanding it once will save you from the app-switching cycle that a lot of people spend years in.

Prayer times are computed, not looked up

There is no database of prayer times. There is a calculation, performed from your latitude, longitude, date and time zone, based on the position of the sun.

Three of the five are unambiguous. Dhuhr is when the sun crosses its highest point. Maghrib is sunset. Sunrise bounds the end of Fajr. Astronomy gives these to the second, and every app agrees on them.

The disagreements are entirely concentrated in Fajr, Isha and Asr. Each for a different reason.

Fajr and Isha: it's an angle

Fajr begins at true dawn, when light first appears. But "first light" is a continuum, not an instant, so it is defined by how far the sun sits below the horizon — the twilight angle.

Different authorities settled on different angles, based on observation in different places. The commonly used values:

A larger Fajr angle means the sun is further below the horizon, which happens earlier — so a bigger angle gives an earlier Fajr. The difference between 15° and 19.5° is easily fifteen to twenty minutes.

That is your eleven-minute discrepancy. Two apps shipping different regional defaults.

Asr: it's a shadow, and a school

Asr is defined by shadow length rather than a solar angle, and here the difference is one of fiqh rather than observation.

• Majority position (Shafi'i, Maliki, Hanbali): Asr begins when an object's shadow equals its own height, plus whatever shadow it had at noon.
• Hanafi position: Asr begins when the shadow reaches twice the object's height, plus the noon shadow.

This is not a rounding difference. Hanafi Asr is commonly 40 to 90 minutes later, varying with season and latitude. For most Bangladeshi families the Hanafi setting is the relevant one — and an app defaulting to the majority position will look badly wrong to them, through no fault of its arithmetic.

Almost every "this app's times are wrong" complaint is a convention mismatch, not an error. The app is answering a slightly different question than the one you're asking.

High latitudes: where the calculation runs out

If you live in London, Toronto, Stockholm or anywhere above roughly 48° latitude, there are weeks in summer when the sun simply never goes 18° below the horizon. The equation has no solution. There is no moment that satisfies the definition.

Apps then apply an approximation rule, and the choice of rule is another place they diverge:

• Middle of the night — split the interval between sunset and sunrise; Isha and Fajr sit either side of the midpoint.
• One-seventh of the night — allocate a seventh of the night to Isha and a seventh to Fajr.
• Nearest latitude — borrow the times from the closest latitude where the angle does occur, usually 45°.
• Angle-based — scale the twilight period by the configured angle.

In these regions, community consensus matters more than any default. This is precisely where asking the local mosque stops being polite advice and becomes the actual answer.

So why doesn't it match my mosque?

Four reasons, in order of likelihood:

1. Different convention. Ask which method and Asr school the mosque uses, then set your app to match. This resolves the large majority of cases.
2. Deliberate safety margin. Many mosques add a few minutes to the calculated time before calling the adhan. That margin is a decision, not a discrepancy.
3. Jamaat time, not entry time. The printed timetable often shows when congregational prayer starts, which is deliberately later than when the window opens. These are different things being compared.
4. Location precision. A city-level location versus your actual coordinates can shift times by a minute or two. Rarely the culprit for a large gap.

What to actually do

Once, when you install an app — or today, if you've been quietly annoyed for months:

1. Ask your mosque which calculation method they use. One question.
2. Set that method in the app.
3. Set the Asr school to match your madhhab.
4. If you're above 48°, ask which high-latitude rule the community follows.
5. Compare against the mosque timetable for a week, allowing for their safety margin.

Then stop switching apps. The app was almost certainly never the problem; the default was. Pick one that lets you set the convention explicitly rather than hiding it, set it once, and move on.

One note on the Qibla

The Qibla direction is a great-circle bearing to Makkah — exact, and computable from your coordinates alone. If your compass looks wrong, the calculation isn't at fault; the phone's magnetometer is. Calibrate it with a figure-eight motion, and step away from cars, laptops, speakers and reinforced concrete before trusting the needle.