Many Muslims throughout the world utilize websites and mobile apps to determine their prayer and fasting times. Hidden in the settings of these programs is an option to choose the ‘calculation method’ for the angle of Fajr and ʿIshā’. The app ‘pray watch’ for iOS is a good example showing eight different methods:

Calculation MethodFajr AngleʿIshā’ Angle
Muslim World League18°17°
Islamic Society of North America [ISNA]15°15°
Egyptian General Authority of Survey19.5°17.5°
Union of Islamic Orgs of France [UOIF]12°12°
University of Islamic Sciences, Karachi18°18°
Shia Ithna-Ashari, Leva Inst., Qum16°14°
Majlis Ugama Islam Singapura20°18°

Most users of these applications, and even scholars, may be unaware what these numbers represent and which method to select. In fact, often people may never even notice the option to change the calculation method and just use the default preset for each program/app.

Some users might choose the country they live in, falsely assuming these calculations were meant for their specific region. So someone living in France may choose UOIF and another person living in America may choose ISNA. Yet another group of users might falsely assume that different calculation methods represent most scholars living in a specific country. So someone who trusts Egyptian scholars to be more accurate in their research on Islam may choose the Egyptian General Authority of Survey, even if they live in America, and another fellow American might choose the University of Islamic Sciences, Karachi if they think the scholars of Pakistan are more diligent and reliable. Both assumptions are completely unfounded.  

The impact of these differences on the timing of the prayers can be very significant. At 20° for Fajr in Anaheim, California the time enters at 4:01 AM while using 12° results in 4:49 AM. That is a difference of almost an hour. In a region even further away from the equator like Vancouver, Canada the difference can reach almost two hours. It is important to understand how these angles came to be used and to what extent they accurately predict the correct timings of prayer.


Both prayer and fasting are pillars of Islam and therefore care must be taken to ensure they are performed properly. Knowing the correct time to start both these acts of worship is essential. If someone prayed before the entrance for the time of Fajr their prayer is considered invalid. Likewise, if someone kept eating after the entrance of Fajr time their fast is invalid. Therefore, utilizing these calculations presents a serious dilemma for those who take prayer and fasting seriously.

Part of the problem lies in the false assumption many people have, several scholars included, that using a fixed degree calculation in a particular region will yield an accurate prayer time. This presumption is built on the idea that technology has advanced so much today that we are able to precisely determine the timings of all prayers based on the angle of the sun above or below the horizon. Such a notion, however, is severely mistaken and based on an ignorance of how prayer times are actually determined in the first place.

How Prayer Times are Defined

The start time for the five daily prayers are summarized in the following chart:

PrayerStart Time
FajrDawn: when a line of light first appears and begins to spread across the horizon
ẒuhrAfter midday: when the sun has crossed its highest point and has begun to decline
ʿAsrWhen the shadow of an object, minus its shadow at noon, equals the object itself [or twice the object according to Imam Abū Ḥanīfah]
MaghribSunset: when the disc of the sun has gone below the horizon
ʿIshā’When the reddish glow has disappeared from the sky after sunset [or whitish glow according to Imam Abū Ḥanīfah]

During the time of the Prophet Muhammad people would observe the shadow of the sun or the amount of light in the sky to determine the prayer timings. As can be seen from the chart above, the timings for Ẓuhr, ʿAsr, and Maghrib are dependent on the position of the sun. This is more scientifically deterministic and can be calculated more accurately than dawn or dusk.[1] However, the timings for Fajr and ʿIshā’ are not directly dependent on the position of the sun but rather on the amount of light in the sky. That amount of light is not scientifically predictable for each location on Earth since it varies by season, altitude, location, geographical barriers, and other factors.

Definitions of Twilight and Solar Altitude

People are naturally interested in the amount of light that exists in the sky before and after sunset. This light is known as twilight and is produced by the reflection and scattering of sunlight towards the horizon of an observer on Earth. Determining the amount of twilight helps people decide when to turn on or turn off their street lights, and has many other uses. Scientists have categorized the amount of twilight that should exist into three distinct phases. Civil twilight [6 degrees] is the stage where the horizon is clearly visible at sea level and there is enough luminance to enable outdoor civil activity without the need for street lights. Nautical twilight [12 degrees] is when the horizon at sea level is no longer visible and altitudes cannot be determined by referring to the horizon. Astronomical twilight [18 degrees] indicates the change from night to day, and vice versa.

When calculating Fajr and ʿIshā’ prayer times, people use various degrees of the angle of the sun to approximate those times. Some have tried to align with the scientific definitions of various stages of twilight. However, all these calculations are misleading for determining prayer times because they do not align with the Islamic definitions of when Fajr prayer comes in, which is: when a line of light first appears and begins to spread across the horizon. Therefore, we should clearly differentiate between ‘Islamic dawn’ and ‘astronomical twilight’.

Factors that Affect Observation of Prayer Times

Observations of twilight at various locations on earth have made it clear that it is incorrect to assume a fixed degree calculation for the start of Fajr and ʿIshā’ prayers. The reported solar depression angle usually can fall anywhere between 12° to 18° [or even between 9° to 20°]. However, there are many factors that affect the timings of dawn and evening twilight:

  • Season: Several observation reports in the same region have indicated that degrees of the sun below the horizon for Fajr and ʿIshā’ varies throughout the year.  
  • Latitude: Several observation reports indicate that the further away from the equator a location is, the more variance there will be.
  • Altitude: Regions throughout the earth have different altitudes, and this affects the observation for twilight. Most calculations assume zero feet above sea level, resulting in inaccuracies. Even the time for sunset, which is much more deterministic than twilight, can be different in the same city depending on whether a person is on a hill or in a valley.[2] If that is the case for sunset, then the variation at twilight would likely be even greater.
  • Obstructions: Many people live in areas where hills or mountains block a clear view of the horizon. This results in significantly different timings for those who cannot get a clear view of the horizon without traveling a great distance. Whether or not this should be taken into consideration is a matter or disagreement among Muslims scholars.
  • Light Pollution[3]/Clouds: The true light from the sun during dawn will be seen above the light pollution or clouds at a later time, thus giving a lower degree calculation for Fajr. Whether or not this should be taken into consideration is a matter or disagreement among Muslims scholars.
  • Observer: It has been noted that inexperienced observers generally tend to see the light on the horizon later since their eyes are not used to it and it is often not clear to them what to expect and what to look for. This will naturally skew the observations that are reported.

The following is a brief list of different documented observations for Fajr in various parts of the world to confirm the previous point:

  • A group of scholars from the UK in 1983 documented various observations throughout the country as falling between 12° to 16°.[4]
  • In 1985, a group of scholars in Chicago concluded that their observations for dawn fell between 13° to 15°.[5]
  • Various observations in the USA and Canada indicated Islamic twilight between 12° to 15°.[6]
  • In 2004, observations for the entire year in Riyadh, led by Shaykh Abdul-Aziz Fauzan, indicated that dawn fell at 15°.[7]
  • In 1988, Hizbul Ulama in the UK compiled a report after performing daily observations for an entire year. Their observations fluctuated throughout the year between 12° to 18°.[8]
  • Moonsighting.com collected data from different observers in the USA and Canada over decades which indicated a range of 14.8 to 17.5° for Fajr and 11.2 to 17.6° for ʿIshā’.

Choosing an Approximate Calculation for Facilitation

Since the angle of the sun below the horizon is not constant for determining ‘Islamic dawn’, there are several options that Muslim legal scholars have considered:

  1. Recommend that every region utilize local observations to determine the prayer times and report it to the rest of the community. This would be extremely difficult for people living in cities where there are several obstructions and light pollution since it would need to be done several times throughout the year and would still vary drastically depending on the location of observation. This method would also be near-impossible for certain people who are unable to observe the horizon in their circumstances.
  2. Use the definition of Astronomical Dawn for Fajr prayer calculation.[9] However, this would be incorrect since the start of Fajr does not equate to the criteria of Astronomical Dawn.
  3. Go with the highest or lowest timing to be on the ‘safe’ side. However, this results in a conflict for the start of fasting. By taking the highest degrees for the start of Fajr prayer, to be on the ‘safe’ side, the start of fasting becomes on the ‘dangerous’ side, and vice versa.
  4. Create two separate times for the start of Fajr and the start of fasting. For example, using 18 degrees for the start of fasting and 12 degrees for the start of Fajr prayer. This method is problematic for two reasons. One, the time for the beginning of fasting and Fajr prayer is the same. Two, these two times could vary by as much as one or two hours in some regions, resulting in confusion and difficulty for people.
  5. Choose an approximate time for each region, or for all regions, knowing that it is not entirely precise, and inform people to adjust based on their own casual local observations.[10] A good approximation would be 15° because it is the middle point between twelve and eighteen, which is usually the range of dawn for most places on Earth.[11] While someone is using the 15° calculation for both Fajr and ʿIshā’, they may look outside and if they notice that dawn or dusk is different from the computed calculation they should appropriately adjust for that. Such an adjustment is expected to be rare because most people living in cities cannot easily view dawn from the locations they would normally pray at. When in doubt follow your trusted local scholar or institution for the adjustments they have made. This is the opinion that is recommended.


Since most people live in cities today, there are many factors which prevent them from correctly observing dawn to determine the start of Fajr prayer. It is still quite easy to ‘primitively’ observe the other four prayer times without any computer programs, but Fajr seems to be the exception since it is often difficult to get a clear view of the horizon. There are several incorrect assumptions people have about Fajr and ʿIshā’ prayer times, the most important of which are: that Astronomical Twilight is equivalent to the start of Fajr, that fixed degrees are static in one particular region, that fixed degrees apply across all different regions, that calculation methods were developed for the specific regions which issued the ruling, and that the prayer times can be precisely known just through generic calculations. None of this is true. The solution to this dilemma will either be to insist on accurately calculating the time for each location on Earth or to adopt an approximate calculation due to the fluctuating nature of dawn and evening twilight. The second approach is preferred due to the severe difficulty created by the first in our day and age.

Written by: Shaykh Mustafa Umar


After thanking Allah, I would like to thank Dr. Muhammad Aslam Khan for his painstaking effort in compiling an unpublished research paper entitled “Problems and Prospects of Muslim Prayer Times Calculation”. This served as my primary resource for framing the issue. I am also grateful to Dr. Khalid Shaukat of moonsighting.com for his valuable discussions with me on the subject, to Dr. Ahmad Salama of Jet Propulsion Laboratories who patiently put up with my numerous interrogations and for suggesting the default fifteen degree approximate calculation, to Dr. Yasir Qadhi for insisting that I add several footnotes addressing common contentions against the fifteen degree calculation, and to Shaykh Muneeb Baig who organized several trips into the California desert and established an unparalleled sighting methodology with multiple observers, DSLR cameras, topography maps, and more.  

[1] Even a more precise calculation like the timing of sunset may be off due to refraction and other factors. “Although noon at any place on the Earth can be predicted with an accuracy of 0.1 second, sunrise and sunset have an uncertainty of minutes because of unpredictable refraction of rays of light near horizon…The observed sunrise is advanced and the observed sunset is delayed due to the refraction of light…all the computer programs assume a nominal horizontal refraction of 0.567° for estimating.” See Akbar Ali Saifee, How accurate are the computed timings for sunrise and sunset?, www.icoproject.org/pdf/saifee_2106.pdf

[2] Even sunrise and sunset, which are more scientifically predictable, are affected by elevation. The greatest sunrise and sunset elevation effect on Earth is Mount Everest, located at 27.988056 N latitude and 86.925278 E longitude, and has an elevation of 29, 029 feet (8,848 Meters). Sunrise has been calculated to be up to 15 minutes and 31 seconds earlier on Mount Everest than on sea level. The range of the seasonal effect has been calculated to be from 15 minutes and 31 seconds on June 22nd, to a ‘low’ of 13 minutes 41 seconds earlier on March 18th. See www.kosherjava.com/2010/03/07/faq-how-much-earlier-is-sunrise-on-mount-everest-due-to-elevation, last accessed 8-16-2020.

[3] Light pollution is the presence of obtrusive artificial light in the night environment and washes out starlight in the night sky as well as interferes with the observation of twilight.

[4] See moonsighting.com/faq_pt.html section 2.2, last accessed 9-18-2020.

[5] Ibid.

[6] Ibid.

[7] Ibid.

[8] Yaqub Miftahi, Fajar and Isha Times & Twilight (Hizbul Ulama, UK), see www.hizbululama.org.uk/files/fazar_&_isha_times.pdf

[9] This position has even been attributed to premodern Muslim astronomers as argued by Ilyas: “Indeed, 18 degree depression was a commonly used value for fajr and isha in the medieval period, when it must have been based on careful observations.” See Mohammad Ilyas, Astronomy of Islamic Times for the Twenty-first Century (Mansell, 1989), p. 56. However, this is a weak assumption as explained by David King: “I am not aware of any legal text in which it is suggested that one should consult an astronomer on the prayer times or use any of the astronomical tables or instruments that were available for this purpose. It would be naïve to suppose that there was any reason why a legal scholar should have consulted an astronomer.” See David King, In Synchrony With the Heavens (Brill, 2013), p. 468

[10] A ‘casual’ observation refers to a person looking outside from a location which they are used to being at whereas a ‘formal’ observation is a concerted effort to travel to an ideal location to sight ‘Islamic twilight’.

[11] It may be argued that no premodern astronomers identified ‘Islamic twilight’ at 15 degrees or lower as argued by Ilyas: “[David] King [in his book ‘In Synchrony With the Heavens’] has confirmed…no record has been found of the use of a value as small as 15 degrees.” See Mohammad Ilyas, Astronomy of Islamic Times for the Twenty-first Century (Mansell, 1989), p. 56. The first objection to this is that Jaghmini [d. 1344 CE] and Al-Barjandi [d. 1528 CE] have recorded 15 degrees for ‘Islamic twilight’. The second, and more important, response is that the calculations of premodern astronomers were probably different than those used by contemporary astronomers as opined by Yusuf: “Lastly, and perhaps most importantly, they may not have been directly measuring solar depression at all, but rather stellar elevation and (at most) inferring solar depression from it…this is not how twilight angles are determined in modern times. A classical astronomical text citing 18 degrees for true dawn is likely referring to the angle of elevation of a particular star above the opposite horizon from the Sun. A modern discussion is referring to actual solar depression as determined by a different set of calculations. It may be that these are exact parallels, but this needs to be clearly determined, especially given the fact that the relationship between the Sun and the other celestial bodies is not fixed.” See Asim Yusuf, Shedding Light on the Dawn (Nur al-Habib Productions, 2017), p. 199.