Moreover...

Moreover, many sermons and traditions have been related from Amir al-Mu’minin (peace be upon him) in which both the length of the period during which one must await the reappearance and the great events and severe trials of the believers have been referred to. With the existence of this, how is it possible to say that a singly-narrated, forged traditions that says that the Imam specified the time of reappearance as the year 70 A.H. is reliable.

In addition, alteration in Divine decrees is a conceivable matter, though this does not mean that Allah the Exalted is unaware of affairs in the beginning and then acquires knowledge of them. Such a belief is invalid according to the Shi‘a, since all Shi‘a believe Allah to be free and far removed from ignorance coming to know about something after its being concealed.

Bada’ , in the conception which the Shi‘a believe in, is a Qur’anic and Islamic principle, and an important part of the issues of theology and similarly the issues of prophecy are based on it.