Ever compared two prayer-times apps and found their Fajr a few minutes apart? It rarely means one of them is "broken". The difference almost always comes from the calculation method each one uses. Understanding the method is the key to why a schedule lines up with the mosques around you — or drifts away from them.
Fajr and Isha depend on an "angle"
Dhuhr, Asr, and Maghrib are fixed by positions of the sun you can see: passing its peak, the length of a shadow, and sunset. So almost every method agrees on those three.
The ones that differ are Fajr and Isha. They are marked by the light of dawn and the fading of the evening twilight — expressed as an angle of the sun below the horizon. Each authority uses a slightly different angle, and that is where those few minutes come from.
The Kemenag method: Fajr 20°, Isha 18°
In Indonesia, the most widely used reference is the method of the Ministry of Religious Affairs (Kemenag):
- Fajr at an angle of 20° below the eastern horizon.
- Isha at an angle of 18° below the western horizon.
- Asr following the Shafi'i school (shadow = object's height + its noon shadow).
- Ihtiyati — a safety margin of about 2 minutes, so a time is never announced too early.
Compare that with common international methods (MWL at 18°/17°, or Umm al-Qura at 18.5°): different angles produce Fajr and Isha a few minutes away from what mosques across Indonesia usually announce. So an app running a foreign "default" method can leave your schedule feeling out of step with everyone around you.
Why the matching method matters
A few minutes sounds trivial, but at Fajr it means you could start your fast too early, or pray before the time has truly entered. That is why a good schedule doesn't only compute from your city's coordinates — it also uses the method that matches where you live.
Computed, then checked against official data
Computing with the right method is only half the story; the other half is proving the result. Five Prayers A Day computes times directly from your city's coordinates using the Kemenag method (Fajr 20°, Isha 18°), and the results are then matched against Kemenag's officially published times to within ±1 minute for hundreds of cities across Indonesia — all three time zones, from Aceh to Papua.
To be clear: this app is not an official product and is not affiliated with Kemenag. It uses the method Kemenag documents publicly and verifies its output against the official schedule. And as always — where the app and your local mosque disagree, follow your mosque.