Prayer times near me: why your city’s timetable isn’t yours
Searching for the nearest city is a reasonable instinct. It is also how people end up praying to a timetable computed for somewhere they are not.
A city is a point, not an area
Every published city timetable is calculated for a single set of coordinates — usually the historic centre. That is fine if you live there. Greater Paris is about forty kilometres across, which works out to roughly two minutes between its eastern and western edges: small enough to ignore.
Distance between cities is a different matter. One degree of longitude is four minutes of solar time. Paris sits at 2.4° east, Strasbourg at 7.8° — five and a half degrees apart, on the same national clock, which is about twenty-two minutes in every prayer. A Paris timetable is not an approximation for Strasbourg; it is the wrong answer.
Longitude moves the clock, latitude moves the season
These two get conflated, and they behave completely differently. Moving east or west shifts every prayer by the same amount, all year round — a flat offset. Moving north or south barely changes today’s times but changes how much they swing between summer and winter.
That is why two cities can agree perfectly in March and be half an hour apart in June. It is also why a mosque timetable from a city at your longitude but a different latitude will be right for a few weeks and then quietly wrong.
The horizon in front of you is not the one in the maths
Sunrise and sunset calculations assume a flat horizon at sea level. Almost nobody has one. If there are hills to your east, the sun you can actually see clears them later than the calculation says. If you are on the twentieth floor, you see it set later than someone at street level in the same building.
This is not an error in the calculation; it is a difference between the geometric horizon and the visible one. It matters most for Maghrib, where a few minutes is the difference between breaking a fast early and breaking it on time.
Calculated on the device, or looked up on a server
Most apps send your coordinates to a server and get times back. That works, and it also means your location — the most sensitive thing your phone knows about you — leaves the device several times a day, to a company you have not met.
The arithmetic is not hard. The sun’s position for a given time and place is a solved problem, and a phone from a decade ago can do it in milliseconds. An app that calculates locally needs no network, works in a basement or on a plane, and has nothing to send anywhere.
What it cannot do is tell you what your mosque has printed. Where a local timetable exists, that is the one to pray by; a calculation is for the days you are somewhere else.