Fiqh & astronomy · fatwa-backed

Thuluth al-layl — the third-of-the-night method and its justification

In summer the sun in Central Europe reaches neither −18° (Fajr) nor −17° (ʿIshāʾ) for weeks: evening twilight merges into morning twilight without true night — the signs are “disturbed”. For exactly this case, thuluth al-layl (a third of the night) is this app’s default method. Here are its idea, its algorithm and its fiqh justification.

The jump objection against aqrab al-bilād

The classical fallback aqrab al-bilād adopts the times of the nearest latitude where the signs still appear. That is legitimate — but it has a practical price: entering and leaving the bright season produces a jump in the prayer timetable, because a foreign sky is suddenly being computed. Thuluth al-layl was introduced precisely to avoid this jump: the method stays with the local sky and changes only by minutes from night to night.

The idea: dividing the night into thirds of depth

The anchor is solar midnight — the point where evening twilight passes into morning twilight and the sun reaches its deepest depression D. What is divided is not time but depth: ʿIshāʾ falls at the end of the first astronomical third of the night (sun at ⅔·D on the way down), Fajr at the beginning of the third (⅔·D on the way up).

The fatwa’s algorithm in five steps:

1. For each night compute the deepest solar depression D and take ⅔ of it (two thirds of half the night are one third of the night).
2. If ⅔·D is at 18° or deeper → compute Fajr normally at 18°.
3. If ⅔·D is at 17° or deeper → compute ʿIshāʾ normally at 17°.
4. Otherwise compute Fajr at the ⅔ angle (disturbance of the sign: D below 27°).
5. Otherwise compute ʿIshāʾ at the ⅔ angle (disturbance of the sign: D below 25.5°).

Because the substitute angle is derived from the local sky every night, the transition is continuous: at ⅔·D = standard angle both are identical — the timetable glides into and out of the taqdīr period without a kink.

The fiqh justification (fatwa of al-Qara Dāghī, Ramadan 1439)

The method is backed by a fatwa of Prof. Dr. ʿAlī Muḥyī al-Dīn al-Qara Dāghī (Doha, 5 Ramadan 1439 / 21 May 2018), conveyed by the European Council for Fatwa and Research in response to the Aachen inquiry. It sorts prayer times into three cases: (1) the signs appear → the texts apply directly; (2) the signs are entirely absent (polar day/night) → pure taqdīr per the Dajjāl hadith; (3) the signs are disturbed — individual times such as ʿIshāʾ and Fajr drop out: Central Europe’s summer case.

For case 3 the fatwa holds: the ruling is ijtihād-based, not fixed by text — scientifically and astronomically grounded solutions are admissible as long as no definitive text is violated. Where evidences are equal, preference goes to facilitation (taysīr), an explicit objective of the Sharia (“Make things easy, do not make them hard …” — Bukhārī 6125, Muslim 1734; “God intends ease for you …” — Q 2:185). The default remains 18°/17°; one departs from it only when needed and for sound reasons.

The night keeps its function as rest (sakan): because the sun moves slowly near its lowest point, the middle third of depth is the longest in time — in Aachen on 21 June 2018 about 4¼ hours of a roughly 7-hour night, versus about 1½ hours for each outer third.

The fatwa’s evaluation criteria: the substitute is used only when needed (a); the protected core of the night is preserved (b).

How the method came about — the Aachen workshop

Behind the method lie decades of community work: since the 1980s the Islamic Centre Aachen (IZA) under Prof. Dr. Mohammad Hawari issued prayer times for numerous communities across Europe. Above ±45° his algorithm used a ratio variant of aqrab al-bilād (reference latitude 45°) all year round. The IZA’s later-founded prayer-times working group, however, concluded: on days when the astronomical signs really exist, a substitute calculation is not admissible — the signs apply whenever they are present.

The solution emerged at the ECFR symposium “Calculating prayer times in Germany” (Berlin 2016) and the follow-up conference at the IZA (February 2018): there Salim al-Baghā presented the astronomical third-of-the-night method, subsequently confirmed by al-Qara Dāghī’s fatwa. In parallel the physicist Harun Acaroğlu reconstructed the old IZA calculation and identified the necessary corrections — solar parallax, the extent of the solar disc, city topology and elevation, atmospheric refraction, the daily variation of declination and the equation of time — classically subsumed under tamkīn. After theoretical review and numerous sighting expeditions, his algorithm with automated tamkīn calculation became the new basis of the IZA calendar; the scientific elaboration appeared in 2025 as a dissertation at Humboldt-Universität zu Berlin.

Context

In resolution 40 (11/1) the ECFR also permits 12° for some European countries besides 18°/17° — the ijtihād space is recognised as plural. Within it, thuluth al-layl takes the methodologically strictest local position: not a fixed compromise angle, but a continuous quantity derived anew each night. The fatwa also stresses: earlier practice under a different ijtihād remains fully valid (cf. Q 2:143), and the unity of the community outweighs the dispute over methods.

This app implements exactly this algorithm as the default of its high-latitude method (“Thuluth al-Layl”). The taqdīr badge in the day view shows on which days the ⅔ angle applied.

This text is a factual introduction, not a fatwa. Your local scholars and community remain authoritative.

More from the knowledge section

The polar problem — where local sighting reaches its limit · Where do 18° and 17° come from? — Twelve centuries of the angle debate · Are the prayers even obligatory then? — The schools’ dispute · Why tamkīn? — A thousand years of precision corrections · Which calendar gets it right? Germany’s prayer-time calendars compared