How Prayer Times Are Calculated and Why They Differ

The basis of prayer times: the sun's position

The five prayer times are governed at their root by the sun's position relative to the horizon, not a fixed clock hour — which is why the Prophet (peace be upon him) defined them by observable astronomical markers: the sun passing its zenith, the length of a shadow, the sun turning yellow and setting, twilight disappearing, and dawn appearing.

Among the most comprehensive texts on this is the hadith of 'Abdullah ibn 'Amr ibn al-'As (may Allah be pleased with them both), from the Prophet (peace be upon him):

From observed markers to astronomical calculation

These markers are precisely described but need direct observation of the sky, which every worshipper could once do simply by looking up. Today they are translated into astronomical coordinates: the sun's angle below the horizon at Fajr and Isha, and the exact moment of zenith and sunset calculated from the sun's actual position for any longitude and latitude at any moment of the year.

Dhuhr, for instance, is the moment the sun crosses the meridian above a given point on Earth, calculated to the second from the sun's apparent motion; Maghrib is the moment the sun's disc fully disappears below the horizon. Neither is disputed between different calculation methods, because both rest on fixed astronomical geometry.

Where the disagreement lies: the Fajr and Isha angles

The real difference between calculation methods is not in Dhuhr, Asr or Maghrib, but specifically in Fajr and Isha, because their markers — true dawn and the disappearance of twilight — are faint light, not a sharp line, so astronomical authorities differ on the exact angle beneath which the sky counts as dark enough.

Each calculation method is therefore expressed as two angles: the Fajr angle and the Isha angle, the number of degrees the sun sits below the horizon at each moment. The larger the angle, the further the time sits from sunrise or sunset — an earlier Fajr and an earlier Isha.

Calculation methods adopted around the world

That is why every Islamic authority or country adopted its own angle based on local observation, giving rise to several well-known calculation methods used by the Azkar app and other prayer-time apps:

Each method has the geographic region it was officially adopted for, though any of them can be used anywhere; the difference between two methods for the same location can reach ten minutes or more, specifically at Fajr and Isha.

• Muslim World League: 18° for Fajr and 17° for Isha — the most widely used worldwide
• Egyptian General Authority of Survey: 19.5° for Fajr and 17.5° for Isha — Egypt, the Levant and Iraq
• Umm al-Qura University, Makkah: 18.5° for Fajr and a fixed 90-minute interval for Isha — Saudi Arabia
• Islamic Society of North America (ISNA): 15° for Fajr and 15° for Isha — North America
• University of Islamic Sciences, Karachi: 18° for Fajr and 18° for Isha — Pakistan and South Asia

Why times diverge more the further from the equator

The gap between calculation methods widens the further a location sits from the equator toward the poles, because the sun there sets and rises at a shallower angle to the horizon, so it takes longer to drop to 15, 18 or 19.5 degrees beneath it — widening the time gap between methods.

In some very high-latitude regions, the sun never drops far enough below the horizon during parts of the year for astronomical dawn to occur at all. Alternative rules were devised for Fajr and Isha there, such as dividing the night from sunset to sunrise into equal portions instead of relying on the sun's angle.

Qibla direction: a completely different calculation

Some conflate calculating prayer times with calculating the qibla direction, but they are different problems: prayer times are a matter of time, dependent on the sun's position in the sky, while the qibla is purely geometric — dependent on Makkah's coordinates (the Kaaba's longitude and latitude) and your own, calculated as the shortest great-circle path between them, regardless of time or season.

That is why the qibla never changes for a fixed location, unlike prayer times, which shift by minutes every day as the sun's position moves through the seasons.

Which method should you choose?

As a rule, a Muslim follows the method officially adopted in his country or used by his local mosque, so his times match the adhan and congregation around him. The Azkar app suggests a method automatically based on your location, with the option to pick a different one manually if you want to match a specific mosque.

For finer control, you can also choose the Asr calculation school (Shafi'i, with a shadow equal to an object's length, or Hanafi, with a shadow twice its length) and the rule used to estimate Fajr and Isha in high-latitude regions, if you live in one.

Anyone moving between two countries that use different methods may notice a gap in the Fajr or Isha time of up to a quarter hour, even at similar latitudes — which alone explains what many notice as a mismatch between the app they're used to at home and another they use while travelling. It's a matter of convention, not an error on either side.