OK - That took some reading.
My studies (a while ago) gave me the understanding that there was one measure which always increased with time: Entropy.
Entropy is the degree of disorder. As time progresses, disorder always increases. Hence time can be said to have real meaning.
There is a corollary to this - entropy increases so long as the universe increases. If the universe "expands" to its maximum and begins to contract, entropy will decrease and therefore (in theoretical terms, at least) time will go backwards to point zero.
I don't know the names of the physicists, philosophers etc. upon whose theories I have drawn, here. I'm better at ideas than facts!
As our own existence is such a brief moment in the universal scale of time/space, we can use the progression of certain items from a state of higher energy to lower energy (i.e. increase in disorder, as the energy is dispersed) to form a linear progression which we call time. For example, atomic clocks (the most "accurate" timepieces) depend on the degeneration of atoms into a lower energetic state to give their "count" of time.
The scale of the passage of time between the smallest point of the universe and the largest point is such that we need not worry about a shift in the rate of degeneration of atoms, or other changes in the rate of entropy increase. So the passage of time remains constant, in any perceptible terms.
(That's the first time I've ever thought about differentiating time by time: TdT !!!).