Modern physics considers Time to be a dimension and combines it with the three distance dimensions into a complexity that it calls SpaceTime.
But the 'dimension' of Time is utterly unlike the dimensions of distance. In a distance dimension we can move backwards and forwards and at a velocity of our choosing. But in the Time'dimension' we cannot move backwards and furthermore are constrained to move forwards at a rate over which we have no control.
Modern physics totally misunderstands Time.
We must therefore think more deeply about Time.
The passage of Time is sensed in movement. What moves, or how fast or slow it moves, is irrelevant. At one end of the scale a unit of light, the photon, moves at 300,000 km/s. At the opposite end of the scale continents drift apart at just 1cm per year. Biological changes to living creatues, such as ourselves, are caused by the slow movement of proteins and fats within the body.
The complexity of Time is purely a consequence of this great variation in the velocity of objects and materials.
Consider, for a moment, a Universe in which everything moved at the same velocity, say at 1m/s. That Universe would be utterly different to the one we see today. But we could then say that one second was always represented by a path length of one meter. We would no longer need the concept of Time, for time is now embedded in the distance dimensions. In mathematical terms we may put t = d/v, time is distance divided by the velocity of movement.
Now you will say that is all very neat but in the real Universe things do not all move at the same velocity.
In the Aether hypothesis Space is a substance. The internal pressure of that substance is the electric potential and its propagation velocity is the gravitational potential. A special matter substance does not exist. Matter, in all its forms, is constructed from very complex variations in the local electric and graviational properties of the Aether. Possibly the fundamental elements of matter are constructed of some form of electric vortex. A matter vortex may, as a whole, be stationary in the Aether but its constituent electric potentials all move at the local speed of light.
It is now possible to see that every thing in the Universe, that is every electric transient, moves at the local speed of light.
In words; Time is a derivative of distance -- related by the speed of light.
The path of the distance moved may be any shape. It may be a straight line or it may me a complex spiral.
The exact paths of the electric transients within matter is not known. Neither is the exact construction of matter known in non-Aether physics.
For our correct understanding of Time we merely require the Aether hypothesis.
The gravitational potential (the speed of light) is not constant throughout Space. The presence of matter slows the local speed of light to create a gravitational potential field. As a consequence the rate of Time is local and varies from place to place in Space. For example Time runs slower at the surface of the Sun relative to here on Earth. But the difference is only two parts in a million. On the surface of a neutron star the difference would be much greater.
Time for a matter body is a little different to d/c. The path of d must be an out and return path. Also distance d is distance in the inertial reference frame (IRF) of the body in question. An IRF is Space as viewed by the body.