The single most misleading concept in physics is that of time.
Although time is a concept that has proven useful to study and predict the behaviour of physical systems (not to mention how, on the human level, it has become an essential concept to organize, synchronize and regulate our activities and interactions) it remains just that; a concept.
Time is a relational concept that allows us to compare events with periodic systems; in other words, clocks. But time has no more effect on reality than the clocks that are used to measure it. In fact, when you think of it, clocks don’t really measure time. Clocks count the number of recurrence of a particular state. For instance, the number of times the pendulum of a clock will go back to a given initial position following a series of causality linked internal states. So clocks do not measure time, they count recurrent states or events.
If clocks do not measure time, what does?
That answer is nothing can. There has never been a measurement of time and none will ever be possible since time is non-physical. Neither has there been or ever will be a measurement of a physical effect of time on reality. Experiments have shown that rates of atomic clocks are affected by speed and gravity, but these are slowing down of clocks and not a slowing of time.
Yet, as useful the concept of time may be, it is not, as generally believed, essential to modeling reality. In fact, taking the concept of time out of our descriptions of reality solves a number of problems.
For instance mass, momentum, speed and energy are intrinsic properties thus different observers will measure the same mass, speed, momentum and energy regardless of the frame of reference they use.
And if time does not exist, neither does time dilation. Time dilation and the implied assumption of space continuum are essential to explain the constancy of the speed of light in special relativity. But neither is necessary in QGD since the constancy of the speed of light follows naturally from the discreteness of space.
Finally, if time does not exist, then although the unification of space (a representation of space to be precise) and time (which is a relational concept) into mathematical space-time provides a useful framework in which we can study the evolution of a system, physical space-time makes no sense.
Time Distance Equivalence
A simpler and physical way to measure the duration of an event is to mark its start and end and measure the absolute distance a photon will simultaneously travel. This provides measurement of duration that is based on actual physical quantities.
Note: The above is an excerpt from Introduction to Quantum-Geometry Dynamics