Shaykh Saalih Al-Fawzaan was asked:
What is the ruling on specific prayer timings as is found in the prayer schedules?
“As for the prayer schedules which are relied upon, then they are used. The prayer schedules that are relied upon are used, like from Umm ul-Qurra with us or the Qatari prayer schedule which is tested and accurate, then they are relied upon. They are relied upon. As for the prayer schedules which are not known who made them, then they are not relied upon. It is not known the mistakes in them and if they are accurate. As for the prayer schedules that are reliable and tested, then these are relied upon. Yes”.
[Sharh Kitab us-Siyaam min Bulugh al-Maram no. 1]
Faisal Ibn Abdul Qaadir Ibn Hassan