Praise be to Allaah.
It is permissible to use timetables that show the times of
prayer so long as it has not been proven that they are wrong. It has been
proven that many of them are wrong – if not all of them – with regard to
Fajr prayer, and some of them are wrong with regard to ‘Isha’. With regard
to Maghrib the mistakes are slight, because it is easy for most people to
know what the right time is, and to figure out the mistakes in them, by
watching the sun themselves.
Whatever the case, the sign of sunset which is when the
fasting person breaks his fast and the time for Maghrib prayer begins is
when the disk of the sun actually disappears behind the horizon, not behind
mountains or buildings.
The Sahaabah (may Allaah be pleased with them) stated the
time of Maghrib as being when the sun disappears in the veil (of night), and
they used different phrases to describe that. Some of them said “the sun
set” and others said “(the sun) had hidden in the veil (of night)” (cf. Saad
328:32) or “the sun disappeared”. These phrases all convey the same meaning,
which is the total disappearance of the sun’s disk.
You do not have to climb up the mountain or to any high
place, rather what is meant by sunset for the place where you live is when
it disappears below the horizon; when it just disappears behind the
mountains, this is not regarded as sunset.
As you cannot see the sun at the time of sunset because of
the mountains, you can know the time of its setting from another sign which
was mentioned by the Messenger (peace and blessings of Allaah be upon
him), which is when darkness comes from the east.
Al-Bukhaari (1954) and Muslim (1100) narrated that ‘Umar ibn
al-Khattaab (may Allaah be pleased with him) said: The Messenger of Allaah
(peace and blessings of Allaah be upon him) said: “When the night comes
from here (the east) and the day departs from here (the west), and the sun
sets, then it is time for the fasting person to break his fast.”
Al-Nawawi said:
With regard to the words of the Prophet (peace and
blessings of Allaah be upon him): “The night comes and the day departs and
the sun sets”, the scholars said: Each of these three implies the other two,
and he mentioned all of them together, because a person may be in a valley
and the like, where he cannot see the sunset, so he has to rely on the
coming of darkness and the disappearance of daylight. And Allaah knows best.
End quote.
If this is not possible either then there is nothing wrong
with relying on timetables, because at least they state the likely time of
the prayer, so long as it has not been proven that they are wrong.
And Allaah knows best.