Dear Eric,
I believe the 'flow of time' is a most important concept in physics. Not to be confused with Prof. Davies human subjective flow, which he mentioned above.
Einstein's relativity has taught us that the flow of time varies across space according to the energy embodied in that space. In this way we can conceptualise the flow of time as a sort of time dilation map of the universe which will generally accord with a gravitational map, but with a twist if you entertain the idea of an aether, as the energy of motion will also be integrated into the time-flow map.
Check out my essay which has a section on time reversal, as well as a new slant on presentism.
Best Regards
Lockie Cresswell