All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
The time of Maghrib begins with the sunset and ends with the disappearance of the red twilight when the time of ‘Ishaa’ prayer starts as clarified in Fataawa 81532 and 82253.
There is no doubt that the time-length of Maghrib prayer differs according to the difference of the seasons of the year especially if a person lives in a country near the North Pole, where the disappearance of the red twilight delays in some seasons of the year.
As regards a person who lives in the city and is unable to define the times of the prayer by eye-sighting, then he should take into consideration the prayer time calendar which a Muslim country issues or which trustworthy Islamic centres issue in non-Muslim countries. It should be noted that the Islamic centres gave importance to the issue of prayer times, all praise be to Allaah. Similarly, one may rely on the prayer time calendars which are issued by the World Islamic League, Al-Azhar and Karachi Universities, and other trustworthy institutions.
Allaah Knows best.