It is possible to imagine a few scenarios in which time is non-linear. For example, an object could be removed from the present and reappear in the future, or occupy another universe for a duration while simultaneously leaving and returning to a single moment in this universe.
Since all is pre determined (see cause and effect) A => B is already set, this makes the experience of time only a perception of A => X. One can view the experience of time as characters in a movie, they don't know the end but the movie already has one. Linear time is only a perception of A => X.