This is ZindSa's own methodology, written out in public, including the parts that are a convention rather than a citation.
Five of the daily times are defined by where the Sun is relative to your horizon. Sunrise and sunset are the Sun at the horizon. Dhuhr is solar noon, the moment the Sun crosses your meridian, which is not 12:00 on a clock. Asr is defined by shadow length. Fajr and Isha are twilight: the Sun a certain number of degrees below the horizon before dawn and after dusk.
That last one is where methods differ. There is no single agreed angle for the beginning of Fajr or the end of Isha, and different institutions have published different figures. Every prayer-time app has to pick one, and the honest thing is to say which.
University of Islamic Sciences, Karachi: Fajr at 18° and Isha at 18°. This is the shipped default and it is calculated on your own device, there is no prayer-times API in the app, and the whole computation runs offline from your latitude, longitude and date.
Those two 18° angles are not adjustable in Settings. That is a deliberate limitation, and the next-but-one section explains why.
Asr is reckoned by shadow factor: the time when an object's shadow reaches its own length plus its noon shadow (factor 1) or twice its length plus its noon shadow (factor 2). Factor 1 is the standard reckoning followed in the Shafi'i, Maliki and Hanbali schools; factor 2 is the Hanafi reckoning.
ZindSa ships both, and you pick in Settings. Hanafi is the default, because it is the more widely used of the two in India, not because it is treated as more correct. Changing the setting changes only the Asr time; the Fajr and Isha angles stay at 18° either way. One clarification the code makes explicitly: this is an Asr-school choice and nothing else. It is not offered as, and is not wired to, a Sunni/Shia distinction, Ithna-Ashari practice also reckons Maghrib later than sunset, and ZindSa does not compute that, so calling the standard-Asr option a Shia method would be false.
Maghrib is set 3 minutes after sunset, and Dhuhr 2 minutes after solar noon, as a safety margin. This is the least tidy fact on this page and it is the one most worth stating plainly: those two offsets are common practice, not a cited published figure. No source in this project establishes 3 and 2 as the correct numbers. They are the conventional caution, and they are disclosed as such in the app itself, on the prayer card, not only here.
It would read better to leave that out. Leaving it out would make a convention look like a citation, which is exactly the thing this app exists not to do.
Muslim World League, ISNA, Umm al-Qura, the Egyptian General Authority and the Ja'fari conventions all use different Fajr and Isha angles. None of them are in ZindSa, and the reason recorded in the code is specific: those angles exist nowhere in this project, and adding them would have meant writing numbers down from an agent's recollection rather than from a source.
Under the project's rule an unverifiable number is not shipped at all. So the twilight convention is fixed at Karachi 18°/18° and disclosed on the card, instead of being offered as a menu of choices the app cannot honestly compute. Adding the others is a sourcing job for a named reviewer, not an engineering one. Meanwhile the practical consequence is worth saying: your times may differ by a few minutes from your local mosque, and your local mosque is the authority you actually pray behind.
The qibla is the great-circle bearing from where you are to the Kaaba at 21.4225°N, 39.8262°E, the shortest path over a sphere, which on a flat map does not look like a straight line towards Mecca and is not supposed to.
The subtle part is the compass. A phone's magnetometer gives a heading relative to magnetic north; a great-circle bearing is relative to true north. Subtracting one from the other directly is a frame error, and it is a common one. ZindSa keeps the two formulas as separate, separately testable pieces and reconciles the frames using the local magnetic declination from the device's geomagnetic field model, so the arrow points at the Kaaba rather than at the Kaaba plus your local declination. The whole thing runs on-device; the qibla needs no network at all.
Reproduced verbatim from the note ZindSa shows on the prayer card, here with the default Hanafi Asr:
“Calculated on your device using the University of Islamic Sciences, Karachi method - Fajr and Isha at 18°, with Hanafi Asr. Maghrib is set 3 minutes after sunset and Dhuhr 2 minutes after solar noon as a safety margin; those two offsets are common practice, not a cited published figure. You can change the Asr school in Settings; the 18° twilight angles are not adjustable. Times may differ by a few minutes from your local mosque.”
Related: the prayer-time method in the FAQ, and your kundli on your phone, without giving away your data. All posts.