What is the correct time of maghrib?
The time of maghrib is at sunset. However, Muslim scholars have historically held two different positions as to when sunset occurs, as a result of two conflicting groups of hadith reports:
- Sunset occurs as soon as the entirety of the disc of the sun disappears below the horizon. This definition is in accordance with the astronomical definition of sunset determined by the disappearance of the upper edge of the sun – also called the upper limb. 
- Sunset occurs at the apparent descent of the sun and the accompanying atmospheric effects i.e. when the redness from the eastern sky has passed from above one’s head. This occurs some time after the disappearance of the disk of the sun, and results in a delay in the commencement of the time for maghrib prayers.
Sunset or time of maghrib occurs as soon as the entirety of the disk of the sun disappears below the horizon relative to the ‘location’ of the performer of the prayer.
Accordingly, there is no need to delay the prayer to allow time for the passing of the redness from the eastern sky.
1. The Quran does not stipulate what constitutes the setting of the sun, and therefore it is open to both of the above interpretations of sunset.
2. There is a significant group of hadith narrations that explicitly state that the time of maghrib prayer commences as soon as the sun is set below the horizon. For example, the sixth Imam states, “The time of maghrib is when the sun sets and its disk disappears.”
3. The second group of hadith narrations that have been understood to stipulate the time for maghrib prayer after the passing of the redness from the eastern sky do not satisfactorily substantiate this claim, due to issues with either their transmission or signification when seen in light of the entire body of traditions (i.e. their content is not clear enough).
4. The question regarding delaying the prayer till the passing of the redness from the eastern sky does not seem to have arisen until the first half of the second century, and views on this issue are not attributed to the Prophet or the Imams before this period. Irrespective of the basis for the emergence of this question, these traditions implicitly or explicitly indicate the notion of ‘the disappearance of the redness from the east’ is to ascertain that the sun has indeed set, rather than attempting to redefine sunset as the point of the passing of the eastern redness.
5. The second group of hadith narrations can be contextualized and may have occurred in a context in which the horizon was not clearly visible. Accordingly, the only way to ascertain the time of sunset was to wait until the passing of the redness from the eastern sky.
6. As for the issue of delaying maghrib having become a symbol of Shia faith (Shiʿār al-Shīʿa), this holds no jurisprudential value, as there is no proof within Sharia texts for the authority of ‘the symbol of Shia faith’, and therefore it is non-binding. Furthermore, defining sunset for maghrib prayers as the disappearance of the sun below the horizon has historically been a popular opinion amongst past Shia jurists.
7. Delaying the prayer due to precaution (iḥtiyāṭ) is not necessary when a person can ascertain the actual sunset by way of modern technology.
8. Although the time of maghrib prayer starts as soon as the entirety of the sun disappears below the horizon, it is not harmful if an individual decides to delay offering the maghrib prayer after the passing of the redness from the eastern sky.
 Al-Kāfī, vol. 3, pp.279-280 bāb waqt al-maghrib wal ʿishā’ al-ākhira
 Al-Kāfī, vol. 3, pp. 278-279
 Amālī al-Shaykh al-Ṣadūq, p. 80