Updated 27 October 2026 · 5 min read
For most of the world, the sun sinks far enough below the horizon each night for Fajr and Isha to be calculated directly. North of about 48° latitude, which includes the whole of the UK, Scandinavia, much of Canada and northern Europe, that stops being true for part of the summer.
Why it happens
Fajr and Isha are tied to the sun reaching a set depth below the horizon, commonly 15° to 18° (see calculation methods). Near midsummer in London, at 51.5° north, the sun only gets about 15° below the horizon at its lowest point. In Glasgow it is about 11°. If the sun never reaches 18°, then by a strict 18° rule twilight never ends and Isha, and the next Fajr, never arrive.
The common solutions
- Middle of the night: the night (sunset to sunrise) is split in half. Isha is no later than the midpoint, and Fajr no earlier than it.
- One-seventh of the night: Isha is set at most one-seventh of the night after sunset, and Fajr at most one-seventh before sunrise.
- Twilight angle: the portion of the night used is proportional to the twilight angle, for example 18/60 of the night for an 18° method.
- Moonsighting Committee seasonal rule: uses observations from different seasons and latitudes to adjust Fajr and Isha smoothly through the year. It is widely used in the UK.
- Nearest latitude or nearest day: some scholars use the times of a nearby place or date where the twilight does end.
NextSalahClock's “Auto” setting uses the rule recommended for the city's latitude: one-seventh of the night above 48°, middle of the night below. You can choose any rule in Settings.
Where the sun does not set at all
Inside the Arctic Circle, for example Tromsø in Norway, the sun stays above the horizon for weeks in summer and below it in winter. There is no sunset, so no Maghrib can be calculated in the usual way. On those dates NextSalahClock uses the Aqrab al-Yawm convention, taking the times from the nearest date that has a normal sunrise and sunset, and says clearly on the page that it has done so.
What to do in practice
High-latitude rules are a matter of scholarly judgement, and communities differ. If you live in the UK or a similar latitude, the most reliable guide is your local mosque's timetable. Match it using the high-latitude rule, method and minute adjustments in Settings.
Times in this guide are calculated start times. Your mosque may publish different times or iqamah times; see our calculation disclaimer.