The one-sentence version: prayer times are scholarly conventions applied to astronomy. The authoritative schedule for your congregation is the one your local mosque publishes.
Methods differ, by design
There is no single worldwide formula. Fajr twilight is taken as 15° (ISNA), 18° (MWL, Karachi), 18.5° (Umm al-Qura), 19.5° (Egypt), 20° (Singapore), and so on. These are legitimate, established conventions held by different religious authorities. Changing method can shift Fajr or Isha by 10–30 minutes. NextSalahClock shows which method is in use on every result and never silently switches it.
Start times vs. iqamah
Every time on this site is a calculated prayer start (adhan) time. Mosques publish iqamah (congregation start) times which are later by a locally chosen amount. NextSalahClock does not display iqamah times.
High latitudes
At extreme latitudes exact twilight times may not exist on some dates. We apply the latitude-recommended approximation (visible in Settings) and disclose any estimate on the page itself. Such estimates approximate the spirit of the convention; they are not “official” times.
Hijri dates and Ramadan/Eid
Hijri dates use the algorithmic Umm al-Qura calendar. Observances dependent on moon sighting (start/end of Ramadan, both Eids) are formally declared by local authorities and can differ by a day from any algorithm. Predicted dates here aid planning; they are not confirmations.
Precision statement
Solar geometry is accurate to well under a minute for the coordinates shown; published times are rounded to the nearest minute, as is universal practice. Small differences vs. official calendars usually trace to a different method, an intentional safety margin, or your mosque's chosen convention; check Settings first.
Related reading: How prayer times are calculated · FAQ · Terms of use.