To determine Isha and Fajr calculations, one needs to calculate the time when the sun is at a certain distance below the horizon. The twilight angle is used for this purpose and it is defined as the angle in degrees of the sun below the horizon, when total darkness begins or ends.
Some organizations' use a fixed time after Maghrib to determine the start of Isha time.
Several standards have been established for determining Fajr and Isha prayer times.
Egyptian General Authority of Survey:
| Region |
Africa, Syria, Iraq, Lebanon, Malaysia, parts of the USA |
| Fajr – twilight angle |
19.5 |
| Isha – twilight angle |
17.5 |
Islamic Society of North America (ISNA):
| Region |
Parts of the USA, Canada, parts of the UK |
| Fajr – twilight angle |
15 |
| Isha – twilight angle |
15 |
Islamic Organisations Union of France:
| Region |
France |
| Fajr – twilight angle |
12, 15 or 18 |
| Isha – twilight angle |
12, 15 or 18 |
Majlis Ugama Islam Singapura:
| Region |
Singapore |
| Fajr – twilight angle |
20 |
| Isha – twilight angle |
18 |
Muslim world league:
| Region |
Europe, Far East, parts of the USA |
| Fajr – twilight angle |
18 |
| Isha – twilight angle |
17 |
Umm Al Qura:
| Region |
The Arabian Peninsula |
| Fajr – twilight angle |
18.5 |
| Isha – twilight angle |
90 minutes after Maghrib (120 minutes during Ramadan) |
University of Islamic sciences, Karachi:
| Region |
Pakistan, Bangladesh, India, Afghanistan, parts of Europe |
| Fajr – twilight angle |
18 |
| Isha – twilight angle |
18 |
