Does the fasting person break their fast at the sound of the Iftar cannon, or at the beginning of the Adhan, or upon bearing witness (to the sunset), and do they cease eating at the sound of the Imsak cannon or at the Adhan?

The basis for following an opinion regarding iftar (breaking the fast) and imsak (commencing the fast) depends on trusting the person whose opinion is being followed, whether it is by the firing of a cannon or the adhan (call to prayer). However, the Sunnah is the adhan. If the muezzin (caller to prayer) is upright and knowledgeable of the time, then it is permissible to follow him, based on the Prophet's (peace be upon him) saying: "The muezzins are trustees." It is not necessary to wait for the two shahadas (declarations of faith) in the adhan; rather, as soon as the trustworthy muezzin begins his adhan, it is permissible to break the fast, just as imsak becomes obligatory immediately upon the adhan's commencement.