Have you ever noticed that Fajr in Jakarta isn't exactly the same as Fajr in Bandung, even though the two cities are close together? Or been surprised to learn that Maghrib in Aceh falls much later than in Surabaya at the very same moment? That isn't an app error. Prayer times really do change from one place to another, and the reason is simple once you know where the numbers come from.
Prayer times follow the sun, not the clock on the wall
The five prayer times are set by the position of the sun in the sky, not by the numbers on a clock. Fajr begins when dawn first breaks, Dhuhr when the sun slips past its highest point, Maghrib when the sun sets, and so on. Because the sun rises and sets at different times depending on where you are, the prayer times shift along with it.
Our clocks divide the whole of Indonesia into just three time zones (WIB, WITA, WIT). But the sun pays no attention to those zone lines — it moves smoothly from east to west. So even within a single time zone, two cities can have different prayer times.
Two things that create the difference
Longitude (east–west position). The sun rises earlier in a city that lies farther east. For every degree of longitude to the west, solar time falls back by about four minutes. Bandung sits a little west of Jakarta, so its sun runs slightly "late" — and its prayer times shift by a few minutes too.
Latitude (north–south position). This is what sometimes makes the gap large. The farther a city is from the equator, the longer or shorter its daylight becomes depending on the season. A city in the far north, like those in Aceh, can have a noticeably bigger swing in Fajr and Maghrib than a city sitting right on the equator.
How big can the gap be?
For cities close to one another, the difference is usually just a few minutes. But those few minutes matter: a Fajr that is five minutes off means you could start your fast too early, or pray before the time has actually entered. For cities far apart, especially on different islands, the gap can stretch to ten minutes or more.
This is why a single schedule for "all of Indonesia" is never quite right. Times have to be calculated for your own city, from that city's coordinates.
The calculation method matters too
Beyond location, there is one more factor: the twilight angles used to mark the start of Fajr and Isha. In Indonesia, the most widely used reference is the method of the Ministry of Religious Affairs (Kemenag) — Fajr at an angle of 20° and Isha at 18°. Apps or websites that use different angles (many international apps use 18°/17°) will produce Fajr and Isha times that sit a few minutes away from the schedule the mosques around you usually announce.
For that reason, a good schedule doesn't just know your city's coordinates — it also uses the method that matches where you live.
The most practical approach
You don't need to work out the sun's angles yourself. There's only one thing to make sure of: that the schedule you rely on is genuinely calculated for your city, with the right method.
This is exactly what Five Prayers A Day was built for. The app computes prayer times directly from your city's coordinates using the Kemenag method (Fajr 20°, Isha 18°), and the numbers have been matched against Kemenag's official published times to within ±1 minute for hundreds of cities across Indonesia — all three time zones, from Aceh to Papua.
One important note: an app is a helper, not an authority. Where the app and your local mosque disagree, follow your mosque. A good app works to stay as close as possible to that schedule — not to replace it.