In this article
You open two prayer-time apps and see a difference of a quarter of an hour or more for Fajr or Isha. Which is right? Usually both are mathematically “correct” — they just use different settings. Understanding them helps you pick what matches your local mosque and your country’s official authority.
How are times calculated astronomically?
Times are derived from the sun’s position relative to your location (latitude and longitude) and the date:
- Dhuhr: just after the sun passes its highest point.
- Maghrib: at sunset.
- Fajr and Isha: when the sun is a certain angle below the horizon — this is where differences begin.
- Asr: based on the length of shadows — another source of difference.
Fajr and Isha angles
Different bodies use different sun-depression angles. Examples of well-known methods:
| Method | Fajr | Isha |
|---|---|---|
| Muslim World League | 18° | 17° |
| Egyptian General Authority of Survey | 19.5° | 17.5° |
| Umm al-Qura (Makkah) | 18.5° | 90 min after Maghrib |
| ISNA (North America) | 15° | 15° |
The larger the angle, the earlier Fajr — so two methods can differ by many minutes. Many countries publish an official calendar through a ministry of religious affairs or similar body, which is the one to follow locally.
Asr: two methods
- Majority (Shafi‘i, Maliki, Hanbali): Asr begins when an object’s shadow equals its length, plus the shadow at noon.
- Hanafi: when the shadow is twice the object’s length, so Asr is usually later.
High-latitude locations
In some northern cities in summer, the sun doesn’t dip low enough for twilight to disappear, making angle-based Fajr and Isha hard to determine. Apps then use approximation rules such as “middle of the night,” “one-seventh of the night” or the nearest moderate latitude.
How to set up the tool
- Open the Prayer Times tool and allow location or choose your city.
- Select the calculation method used in your country.
- Choose the Asr method.
- Compare with your local mosque’s timetable and adjust until they match.
Travelers can use the Qibla Direction tool to find the qibla and the Time Zone Converter to keep track of the difference with family back home.
Bottom line
Differences between apps usually come from Fajr/Isha angles or the Asr method, not calculation errors. Choose your country’s official method, match it with your mosque, and when in doubt, refer to the official authority or scholars.
