Which mosque should be followed in determining prayer times, and is it necessary to repeat the prayer if it was performed in another mosque before the time of the Adhan according to the adopted schedule, especially given the differing methods of calculating prayer times in the Canadian city of Edmonton due to its geographical location?

The time for Isha (night prayer) begins when the red twilight disappears, and the time for Fajr (dawn prayer) begins when the true dawn, whose light spreads across the horizon, becomes evident. The fundamental principle is that prayer is not permissible unless there is certainty or a strong presumption that the time for it has begun. If you are able to discern the prayer times yourself, then act accordingly. Otherwise, follow someone you trust who is knowledgeable about these times. It is not permissible to pray before a strong presumption that the time has begun. If someone prays while doubting whether the time has entered, their prayer is invalid, and it must be repeated by consensus. Knowledge of the entry of the time, or a strong presumption of it, is a condition for the validity of prayer. It is recommended to delay prayer until certainty is achieved. In case of doubt, follow the most reliable and knowledgeable sources regarding the prayer times, and do not pray unless you have certainty or a strong presumption that the time has begun. The Umm Al-Qura calendar is one of the most reliable calendars, and it is advisable to delay the Fajr prayer slightly when following it.