How prayer times are calculated

Prayer times are set by the sun. Each one begins at a specific position of the sun in your sky, so it depends on where you are and on the date: Fajr at true dawn, Dhuhr just after the sun's highest point, Asr when shadows reach a set length, Maghrib at sunset and Isha when the twilight has gone. Apps calculate these from your coordinates, and the main reason two apps disagree is that they use different angles for Fajr and Isha.

إِنَّ الصَّلَاةَ كَانَتْ عَلَى الْمُؤْمِنِينَ كِتَابًا مَّوْقُوتًا

Indeed, prayer has been decreed upon the believers at specified times.

What decides each prayer time?

The times were taught by observation. In the well-known narration of Jibril leading the Prophet ﷺ in prayer on two consecutive days, once at the start of each time and once near its end, the Prophet ﷺ was told that the time of each prayer lies between the two.

The time is what is between these two times.

Today the same sun positions are calculated instead of watched. A calculator needs four things: your latitude, your longitude, the date and your time zone. From those it works out where the sun will be at every moment of your day, then finds the moments that match each prayer's definition.

How is Fajr calculated?

Fajr begins at true dawn, when light first spreads along the horizon, and ends at sunrise. Because the sky starts to brighten while the sun is still below the horizon, Fajr is defined by an angle: how many degrees below the horizon the sun is when that light appears.

Scholars and astronomers have measured that angle differently in different regions, which is where calculation methods come from:

A bigger angle means an earlier Fajr. The gap between 15° and 19.5° can be more than half an hour, which is why it pays to use the method your community follows.

When does Dhuhr start?

Dhuhr begins just after solar noon, the moment the sun crosses its highest point and starts to descend. Calculators find that moment from your longitude and the "equation of time", a small daily correction for the Earth's tilted, elliptical orbit. Many timetables add a minute or two of caution after noon.

How is Asr calculated, and why are there two rules?

Asr is defined by shadow length. At noon every object casts its shortest shadow of the day. Asr begins when the shadow has grown by a set amount beyond that noon shadow:

• Shafi'i, Maliki and Hanbali schools: when an object's shadow equals its own length (plus the noon shadow).
• Hanafi school: when the shadow is twice the object's length (plus the noon shadow).

Both are based on authentic narrations, so neither is a mistake. The Hanafi time is later, often by 30 to 60 minutes. In Istiqama this is the madhab setting.

When do Maghrib and Isha start?

Maghrib begins at sunset, when the upper edge of the sun disappears below the horizon. Isha begins when the twilight left after sunset has gone, which, like Fajr, is defined by an angle below the horizon, or in the Umm al-Qura method by a fixed interval after Maghrib (90 minutes, extended to 120 in Ramadan).

Which calculation method should I use?

Use the one your local mosque or national authority uses, so your times match the adhan you hear. If you don't know, the Muslim World League method is a common default in many countries.

What happens at high latitudes?

Far from the equator, around and above 48° latitude, summer nights can be so short that the sun never sinks far enough for the Fajr or Isha angle. Calculators then estimate those times with a rule:

• Midpoint of the night: Isha can be no later than the middle of the night, and Fajr no earlier than it.
• One-seventh of the night: Isha can be no later than one-seventh of the night after sunset, and Fajr no earlier than one-seventh before sunrise.
• Twilight angle: the night is split in proportion to the angle, so the times stay within the night.

How Istiqama calculates your times

Istiqama calculates every time from the location you set, with the calculation method, madhab and high-latitude rule you choose in Settings, and shows which ones are in use. Your Today screen counts down to the next prayer, and you can log a prayer as prayed while its time is open.

Questions

Why does my app show a different Fajr time from my mosque?

Usually because they use different calculation methods. Fajr depends on how far below the horizon the sun has to be, and methods use angles from 15° to 19.5°. That can move Fajr by more than half an hour. Ask your mosque which method or angle it uses and pick the same one.

Is the Hanafi Asr time wrong if it's later?

No. Both rules come from authentic narrations and are followed by major schools. The Hanafi school starts Asr when a shadow is twice an object's length; the other three schools start it at once its length. Choose the one you follow.

Do I need to set my location for accurate times?

Yes. Prayer times depend on latitude, longitude and the date, so times for the next city over can differ by several minutes.