Why prayer times differ between apps and your mosque

Fajr and Isha depend on an angle someone had to choose

Dhuhr, Asr and Maghrib are tied to the sun’s position in ways that leave little room for disagreement. Fajr and Isha are different: they depend on how far below the horizon the sun sits at first light and last light, and different authorities settled on different angles for that.

The Muslim World League uses 18° for Fajr and 17° for Isha. ISNA, common across North America, uses 15° for both, which makes Fajr later and Isha earlier. Umm al-Qura in Makkah does something different again, fixing Isha at 90 minutes after Maghrib rather than by an angle at all. None of these is an error; they are different conventions, and a ten-minute gap between two timetables usually means nothing more than that.

The practical answer is to set your app to whatever your local mosque follows, and then stop comparing.

Asr is the one that moves by a lot

If every prayer looks close except Asr, and Asr is off by nearly an hour, that is the madhab setting rather than the calculation method.

The Hanafi school places Asr when an object’s shadow reaches twice its midday length; the Shafiʿi, Maliki and Hanbali position uses once. That is a large difference and it is intentional on both sides. Any prayer app worth using lets you choose, and choosing wrongly is the single most common reason someone concludes the times are broken.

Northern latitudes break the maths in summer

Above roughly 48° north, there are weeks in summer when the sun never dips far enough below the horizon for a true astronomical Fajr or Isha to occur at all. Stockholm, and to a lesser extent Berlin and Manchester, hit this every year.

There is no calculation that solves this, only conventions for what to do instead — hold the last valid angle, divide the night into portions, or follow the nearest city where the angle still occurs. Methods designed for high latitudes, such as the Moonsighting Committee approach, handle it more gracefully than the standard ones. If your summer times look strange this far north, that is why.