Marcel,
Isn't it that as "time"/speed of light slows, distance contracts, so that the speed of light remains Constant?
The basic premise is that in the vacuum, the speed of light is the Constant, nothing can go faster. So that in a moving frame, quantum activity has to slow, so the internal activity and external motion don't exceed C. Consequently distance, as measured by physical objects, shrinks, because they shrink. So while the speed of light is constant to that vacuum of space, if you are moving with it, it would still be measured at C, because your sense of space is contracted, relative to how fast your frame is moving. If your frame reaches the speed of light, there is no action possible in that frame, so "time" has stopped. Of course, everything has been converted to light as well.
Now since gravity is equivalent to acceleration, light is slowed by it, but distance is compressed as well. Basically the premise is measurement is foundational and when we measure, we have to measure something, either mass or light, so gravity does compress mass. That's why water pressure is so much higher, the deeper it is. More atoms pushed into smaller spaces. Space contracts.
I think the focus on the measurement ignores what is being measured and the whole process is all backwards, but it is a bit like epicycles. The math worked and was excellent, but the underlaying physics was all messed up, because the earth was only the center of our point of view, not the more universal situation.
I see the vacuum/space as fundamental, as I argued in my contest entry, as well as the relationship f light to it, but time is simply a measure of activity, just like temperature.
So it is asymmetric because action is inertial. Movement is movement. Time is a measure of the change caused by that movement. Future becomes past. Potential, to actual, to residual. Duration is the present, as events come and go.
We have it backward because our point of view is of the sequence of our perceptions drawn from it, so it seems the present is "flowing" past to future, just like it seems the sun and stars rise in the east and set in the west, when it is the earth turing west to east, just as it is future becoming past.