Specific deadline refers to the eternal life existing after death which never ends!
According to the Koran the specific deadline lies in the purpose of the universe:
We have only created Heaven and Earth and whatever lies between them for the truth and for a specific period, while disbelieve are dodging what they have been warranted about. (46:3)
Have they not refracted about themselves? God has only created Heaven and Earth and whatever lies in between them for the truth and till a Specific deadline.
Yet may men disbelieve about meeting their Lord. (30:8)
Anything you have is temporary, while God has is everlasting.(16:96)
There is nothing whose stores are not [controlled] by us, and we send it down only according to a fixed quantity. (15:21)