Einstein’s relativity teaches:
There is no single universal “now.” Different observers can disagree on the order of events if the events are not causally connected. Time is relative to motion and gravity, not absolute. Our experience of time is psychological, not fundamental.
Relativity does not say that:
time flows in a direction,
time “moves,”
time could flow backwards.
Relativity treats time not as something that flows but as a dimension of spacetime. Events are simply located in time.
Time going backwards would mean the broken window would unbreak itself.