How are the Derry/Londonderry prayer times calculated?
We calculate the times astronomically for central Derry/Londonderry (latitude 55.00° N) from the sun’s position each day: Fajr when the sun reaches the method’s dawn angle below the horizon, Dhuhr after solar noon, Asr when an object’s shadow equals its length (twice its length in the Hanafi school), Maghrib at sunset and Isha when twilight disappears. Times across the city differ by a minute or two.
Why do Fajr and Isha vary in summer?
Derry/Londonderry lies north of 53° latitude. For several weeks around June the sun never sinks far enough for twilight to disappear, so the astronomical Isha and Fajr never occur. We use a recognised rule that allots a share of the night based on the angle; some mosques use the last day the sign occurred or a fixed time instead. If your mosque’s summer timetable differs, follow your mosque.
Which method should I choose?
By default we show the Muslim World League method (Fajr 18°, Isha 17°), widely used in prayer apps. Many Arabs are used to the Egyptian method (19.5°, 17.5°) or Umm al-Qura; choose yours above. The difference can reach half an hour for Fajr in summer; your mosque’s timetable is the final reference.
Accuracy against the Adhan reference library: ±2 minutes. The Hijri date uses the Umm al-Qura calendar and may differ by a day from local moon sighting.