إِنَّ الصَّلَاةَ كَانَتْ عَلَى الْمُؤْمِنِينَ كِتَابًا مَّوْقُوتًا
“Indeed, prayer has been decreed upon the believers a timing prescribed.” — Qur'an 4:103
1 — Fajr: the true dawn
Fajr begins at al-fajr al-sadiq (the “true dawn”) — the first horizontal glow that spreads across the horizon — and ends at sunrise. It is distinguished from al-fajr al-kadhib (the “false dawn”), a vertical column of light that appears earlier and then fades. The Qur'an ties the fast and the prayer to this moment: “…until the white thread of dawn becomes distinct to you from the black thread” (2:187).
Astronomically, true dawn is when the sun is a fixed angle below the horizon and its light first reaches the sky. Calculators express this as a depression angle, commonly 18° (or 15°–19.5° depending on the method) below the horizon.
2 — Dhuhr: the sun leaves the zenith
Dhuhr begins just after the sun passes its highest point (the zenith, or zawāl) and starts to decline. The brief moment the sun is exactly overhead is a forbidden time for voluntary prayer; once it has clearly moved past, Dhuhr enters. In modern terms this is solar noon for your longitude plus a small margin, not clock 12:00.
3 — Asr: the shadow method (where the schools differ)
Asr is defined by the length of an object's shadow. Set aside the small shadow an object casts at noon (the “shadow at zawāl”). Then:
- Majority (Maliki, Shafi'i, Hanbali): Asr begins when an object's shadow equals its own length (plus the noon shadow).
- Hanafi: Asr begins when the shadow equals twice the object's length (plus the noon shadow) — so the Hanafi Asr starts later.
This is a genuine, well-known difference of the classical schools; both are valid positions traced to the reports on the Prophet ﷺ. Many calculators offer a “Standard” and a “Hanafi” Asr precisely for this reason.
4 — Maghrib: sunset
Maghrib begins at sunset — when the sun's disc has fully disappeared below the horizon — and this is also when the fasting person breaks the fast. It is the simplest of the five to observe directly. (A small correction for atmospheric refraction and the observer's elevation is applied in precise calculation.)
5 — Isha: the twilight disappears
Isha begins when the lingering red glow of dusk (al-shafaq) fades from the western sky and full night sets in. As with dawn, this maps to a solar depression angle — commonly 17° or 18° below the horizon, depending on the method.
From the sky to the calculator
Every classical sign above corresponds to a measurable position of the sun, so a calculator reproduces the same rulings with geometry — using your latitude, longitude, date, and a chosen calculation method (which simply fixes the Fajr/Isha angles and the Asr shadow ratio):
| Prayer | Classical sign | Modern parameter |
|---|---|---|
| Fajr | True dawn spreads on the horizon | Sun ~15°–19.5° below horizon |
| Sunrise | Upper edge of the sun appears | Sun at horizon (with refraction) |
| Dhuhr | Sun declines past the zenith | Solar noon + margin |
| Asr | Shadow = 1× (or 2× Hanafi) object length | Shadow-ratio factor 1 or 2 |
| Maghrib | Sun's disc fully sets | Sun at horizon (with refraction) |
| Isha | Red twilight disappears | Sun ~17°–18° below horizon |
Common methods (Muslim World League, ISNA, Umm al-Qura, Egyptian Authority) differ only in these angles, which is why the same location can show times a few minutes apart between apps. In far-northern/southern latitudes where twilight may not end before dawn in summer, methods apply an approximation (e.g. “nearest latitude” or “middle of the night”).