There’s a clock that controls time. You can turn the hands of the clock to rewind time, but not fast-forward it. This is used to stay in the game forever.
After rewinding time, nothing is changed except for schedule and playable time. The things you did are still there, what happened to the characters still happened. If I added scheduled events in the future, these events would occur again at their scheduled time.
The first successful attempt at time-manipulation will earn you Master Manipulator.