Earlier quoted context omitted.
I don't think we have any proof that time is steady. It may just appear as steady. Much like clock based games way back when. You could speed up or slow down the clock rate and the game would be run the same. Only a external observer out side of the system would be able to detect the change. Edit. But I guess you were talking about our perception of time.
If there is an outside observer with their own sense of time, how would we know which time is real? Are they both? It would seem that, even if not steady to the outside observer, our time is still steady. In a world where physics depends upon time, is it even possible for time to not be steady?
But you are right, if there was a outside observer the same stands, just for that observers observer -- hypothetically.
> In a world where physics depends upon time, is it even possible for time to not be steady?
I think so. Physics is a construct that we have to describe how our universe works.
Lets think about things in "ticks" where a "tick" is just one particle or I should say interaction happening in our universe. Or better think of our universe as a big state machine. Between each new state there are many ticks arranging the matter and getting ready for the next observed state. And by observed state I mean observed by the universe -- or realized. Now we have two time domains to think about. One, tick time. How long is a tick? Would it matter if some ticks took "longer" than others. Then you have the notion of time outside of a tick, that gives ticks its "tick time" or what makes some ticks "longer" than others. If this is anywhere near the case then time outside of the umbrella of each realized universe state does not matter.
I may not be doing a good job of getting the notion out of my head. But try to think of it if you were in a video game. Lets take it back to maybe the "Max Payne" days given it is a game that has some dealings with time. If you were playing the game on a laptop and closed the lid and the computer suspended would Max be able to detect or care even that the time between rendering one frame the other went from something like 60FPS (well back then 12FPS) to 2 hours our observed time to render the next frame? We would be the hypothetical observer. Max would not have a clue.
Anyways thinking about how time works is always fun. About all we can do is learn how time works from our observable position.