Or maybe time is real. Maybe the mere act of clocks marking time is not time itself.
Hmm...
I am of the staunch belief that time as we know it is a man-made "metaphysical" construct.
God put a TIMEX in the sky - a natural clock made from the periodic motion of the celestial bodies we view on our projection screen we call a sky.
Humans redefined time a myriad of times... over time.
But, this is just futility in practice: trying to gain control of events while at the same time ordering them according to their evolution (read: changes in state.)
God defines "time," as it were, as an evolution of events also. A day is an unspecified period of time; the first day was made when God
separated (evolution of event/change in state) the light from the dark. And, depending on who you talk to, that first "yom" interval was an aeon. Other times, time according to God is dictated by the seasons, moonrise and sunrise.
These are simply evolutions of events - time is a false dimension, and a false construct humans used to try to make sense of evolutions of events. Humans cannot process infinite "now," so we chop up events in extremely small intervals to
distinguish "now" from "now."
We made up the definition, or standard for time. It is arbitrary.
One could try to define time by the movements of a clock I suppose. Ever consider that what moves (any clock) may just be moving as time dictates? Now if time were not the same, then whatever moved would not involve the same time!
In the case of so called atomic clocks, the timepiece is categorically recording a certain number of hyperfine transitions in isotopes. And, that number of transitions is defined by "us" - a (semi)arbitrary figure equated to the SI unit of time. In the same way, the speed of light is defined as the time it takes light to travel one meter - which is why "normal" physical systems take $c=1$ (it allegedly takes light 300 million
ths of a second to travel one meter.)
In other words, we make up the definition of time, and apply it to math and science.
And, yes clocks are suspicious in relativity - particularly because we can not necessarily reproduce and test relativistic time frames in the lab. It has been shown in the lab that time dilation exists, especially between atomic clocks and satellites. But the problem is getting enough matter that "matters" (a complete hydrogen atom, for example) to get to relativistic speeds in the first place.
It comes back down to a matter of
available energy, and the shifts/perturbations in energy as a reflection of the evolution of events. The mathematical (or physical) action function.