  This paper is a continuation of the papers [gr-qc/9409010, gr-qc/9505034,
gr-qc/9603022, gr-qc/9609035] and is devoted to the riddle of the origin of the
arrow of time. The problem of time orientation reduces to that of the
difference between the past and the future. The riddle escapes solution in
deterministic dynamics and in the dynamics of standard indeterministic quantum
theory as well. In the dynamics of indeterministic quantum gravity, the past is
reconstructible uniquely, whereas the future may be forecasted only on a
probabilistic level. Thus the problems of the past and the future and, by the
same token, of time orientation are solved.
