It's futile at best to try to understand the mechanics of what allows there to be a "past", "present", & "future", I
think, considering we exist completely within it & are completely reliant on it.
Of course, one could try to argue with that from a metaphysical PoV, but I don't even know of any such arguments.
But really, "the present" can de defined rather easily, I think, without need for philisophical or scientific rumination.
Simply, it is what is, without consideration of what has been or what will be. This means that the "present" has the same "value"
everywhere, always, irrespective even, of the "speed" of time in different places.
Of course though, everyone in the universe has a different observation of the present, and hence differing perceptions of it,
but I imagine that's already pretty well understood.