Prayer times explained: why Umm al-Qura, MWL and ISNA disagree, and how to match your mosque

Prayer times come from the sun, and the only real argument is where to draw the line for dawn and night. Umm al-Qura, the method behind the official calendar in Saudi Arabia, draws Fajr at 18.5 degrees below the horizon and sets Isha at a fixed 90 minutes after Maghrib. During Ramadan that gap becomes 120 minutes. Every other method draws the lines a little differently, which is why two prayer apps can disagree by 10 minutes and both be following a real method.

The free Cubbbix Prayer Times Calculator computes the times from the sun position for any city and date. It runs in your browser, needs no account, and lets you change the city, the method, the Fajr angle, the Isha rule and the Asr school. The point of all those settings is simple: match the timetable your own mosque follows, instead of arguing with an app that hides its method.

Figure 1: Fajr follows the sun below the horizon, not a fixed clock time.

Why two apps give different Fajr times

Fajr is true dawn, the first horizontal light in the east. Astronomers mark it by the sun depression angle: how far below the horizon the sun sits when dawn starts. Umm al-Qura uses 18.5 degrees. The Muslim World League uses 18. The University of Islamic Sciences in Karachi uses 18. The Egyptian authority uses 19.5. ISNA in North America uses 15. One degree moves Fajr by about 4 to 5 minutes, so the gap between ISNA and Egypt on the same morning can reach 20 minutes.

Isha has the same story in reverse. Most methods use an angle for Isha too, but Umm al-Qura uses a clock interval instead. That choice keeps Isha at a steady distance after Maghrib all year, which suits congregational prayer. It also means Umm al-Qura Isha can sit far from an angle-based Isha in summer, when twilight lasts longer. Neither number is wrong. They answer different questions: one asks when the sky reaches a set darkness, the other asks when the congregation can gather.

Figure 2: The method is the main reason two timetables disagree.

Asr and the two schools

Asr is the one prayer where the schools disagree on the definition itself. Most schools start Asr when an object's shadow equals its own length, measured past the noon shadow. The Hanafi school starts it when the shadow equals twice the object. The gap is about 30 to 45 minutes, and it has nothing to do with your city or your app. If your Asr looks late compared with a friend's, check the school setting first. The calculator has both options for exactly this reason.

How to match your mosque timetable

Pick your city and the Umm al-Qura method if you are in Saudi Arabia, then compare one full day against the mosque timetable. If every prayer is off by the same amount, the UTC offset is wrong: fix that one field and the whole day lines up. If only Fajr or only Isha is off, the method is wrong: try the next method in the list. If only Asr is off, the school setting is wrong. Work through those three checks in that order and you will find the mismatch in under a minute.

One more check matters for travellers. London and New York change their UTC offset with daylight saving time, and Cairo has changed its rules in recent years. A timetable that was right in January can be an hour out in July for those cities. The calculator leaves the offset editable so you can fix it instead of waiting for an app update.

Figure 3: Compare one day first, then trust the sheet.

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