Updated 2 November 2026.
Your mosque’s timetable comes first.
What goes wrong with plain defaults
The code library we use, adhan-js, falls back to “middle of the night” unless told otherwise. For Birmingham on 21 June 2027 that gives Fajr 01:09 and Isha 01:09 under an 18° / 17° setting: the same minute. We don’t start with that. Our UK starting setting gives Fajr 02:44 and Isha 22:55.
That doesn’t make a 01:09 Fajr a mistake in itself. Wifaqul Ulama’s 2026 PDF for Birmingham prints Fajr near that time in June, alongside a much earlier Isha (our matching setting gives 22:36). The problem is a setting nobody chose and nobody stated.
The rules, in plain terms
- Middle of the night: no earlier than halfway between sunset and sunrise.
- One seventh of the night: Fajr no earlier than one seventh of the night before sunrise; Isha no later than one seventh after sunset.
- Twilight angle: a share of the night in proportion to the angle.
- Seasonal limits: the Moonsighting Committee formula sets minutes from sunrise and sunset that change through the year. From 55° north one seventh of the night takes the place of 18°, and it sets the time only when it is nearer to sunrise or sunset than the minutes are, which is about 27 March to 16 September.
The jump at 55° north
The seasonal formula changes at 55° north: below the line it uses seasonal minutes or 18°, and from the line seasonal minutes or one seventh of the night, whichever is nearer to sunrise and sunset. So at the line one seventh sets the time from about 27 March to 16 September in 2027, and the seasonal minutes for the rest of the year. Two places a few kilometres apart, at 54.98° and 55.01° north, get Fajr 02:24 and 03:30 on 22 June 2027: a 66-minute jump. The gap is 30 minutes or more on 105 days of 2027, and Isha moves by up to 24 minutes.
That jump comes from how the formula is written, not from the sky. Nothing we read explains which side of it a place should follow, so for places from 55° (Glasgow, Edinburgh and any typed location) we don’t offer a starting setting. The page shows the range, asks you to choose, and says that your mosque’s timetable comes first. The choice can be cleared.
How we show it
Every screen states the rule in use. A dated banner appears on days the angle isn’t reached, a dotted underline in the month table marks days a limit sets the time, and each city page lists those dates for 2027. If a setting puts Isha and Fajr under 10 minutes apart, the page says so. Above about 65°, days with no sunrise or sunset borrow from the nearest latitude that has them, the usual order of prayers may not hold, and a banner says to use a local timetable.
The UK discussion over 18° is live and public, and we take no side. Compare methods for your own city.