How Prayer Times Are Calculated: The Astronomy Behind the Schedule
Every prayer time on your screen is really a statement about where the sun is. Fajr is "the sun is this far below the horizon." Dhuhr is "the sun just passed its highest point." Maghrib is "the sun just set." The whole daily schedule is celestial mechanics translated into worship — and once you see the geometry, the times stop feeling arbitrary.
Each prayer = a solar position
| Prayer | Astronomical definition |
|---|---|
| Fajr | Dawn: the sun reaches a set angle below the eastern horizon (typically 15°–19.5°, depending on convention) |
| Sunrise | The sun's upper edge appears on the horizon (not a prayer, but it ends the Fajr window) |
| Dhuhr | Just after solar noon — the moment the sun begins to decline from its highest point |
| Asr | When an object's shadow equals its noon shadow plus its own length (×1 or ×2, depending on school) |
| Maghrib | Sunset: the sun's disk fully disappears below the horizon |
| Isha | Night: the sun reaches a set angle below the western horizon (typically 15°–19.5°) |
Why the same city gets different times from different sources
If it's all astronomy, why do two apps disagree by ten minutes? Because two of the definitions involve human choices, not pure physics:
- The Fajr/Isha angle. "Dawn" isn't one instant — it's a gradual brightening. Different organizations define dawn at different solar depressions: 18° (the most common), 15°, 19.5°, and others. A single degree of difference shifts Fajr by roughly 4–5 minutes. This is the biggest source of disagreement you'll see.
- The Asr shadow factor. The majority opinion starts Asr when the shadow equals one object-length beyond noon; the Hanafi school uses two lengths, making Asr later. Both are classical, respected positions.
Neither side is "wrong" — these are legitimate scholarly differences about how to interpret the same natural signs. That's why we always say: confirm with your local mosque's timetable, which follows the convention your community uses.
Why times shift every day
Three moving parts change the schedule daily:
- The Earth's tilt. As we orbit the sun, the sun's path across your sky rises and falls. That's why Fajr is brutally early in summer and Isha stretches past 10pm — and why everything compresses in winter.
- Your latitude. Near the equator, day length barely changes all year, so prayer times are rock-steady. In northern cities, summer days stretch enormously. Above the Arctic Circle, the sun sometimes never sets — scholars have special rulings for those cases (like following the nearest normal-latitude city).
- The equation of time. Solar noon isn't always 12:00 — Earth's elliptical orbit and tilt make it wander by up to ~16 minutes through the year. Dhuhr tracks true solar noon, not clock noon.
How apps actually compute it
Modern prayer-time calculation is a solved problem in spherical trigonometry. Given your latitude, longitude, date, and chosen convention, the formulas compute the sun's declination and the hour angle for each required solar position. It's the same math astronomers use for sunrise/sunset — the prayer-specific part is just the chosen angles.
Our Prayer Times page runs these calculations from your location right in the browser, using widely adopted conventions. No observatory required — just geometry that scholars have refined for over a thousand years, from the zij tables of medieval Baghdad to the code on your phone.