The way I understand it, (which is virtually not at all really!) there is no overall universal time or background clock like a force field of time or "stable rhythm" that everything experiences. But every observer experiences its own time, relative to whatever point of reference is used.
This is where my meager brain fully melts down.....
If everything is moving through spacetime, the faster through space, relative to C, the slower you travel through time, the slower through space, the faster through time.
So if every particle is moving away from each other equally at C, from each ones perspective it's own time is slowed to 0, so now everything is eternally rushing away from everything else with no time passing.
Now my reasoning and vocabulary fail completely tbh,
Surely time had also only just sprung into being so shortly after the big bang? If "everything" was moving near C, there was no "other" time to be relative to?