You're arguing from way off base here. You cannot judge the thing being measured by the unit of its measurement. Indeed, you have completely combined the two in your mind. We can use anything to measure the passage of time, regular astronomical occurrences specific to Earth are the most useful. The Venusian calendar is no more use to us here than on Mars, but neither is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium-133 atom, which is constant everywhere (and is in fact the definition of the second and is used in atomic clocks) except for all the time dilation that occurs in the universe. Time isn't based on our measurements of it! Time already is, and would still be without any humans, as it was before us and will be after us. Our units are for our own convenience and application. They are our map. The territory already existed.
I still don't know what you mean by "solid time". You won't get unchangeable time anywhere, it is slowed by both very high gravity and very high speeds, but only relative to another location without such high gravity or speed. When approaching a black hole you would not notice time slow down, but if you get back out of it you'd find that everyone else's clocks (and even dates) have advanced further than your own. That's how you'd measure it precisely, in any case. Hang around longer and everyone you know will have grown grey in the hair and long in the tooth by the time you return.
The arrow of time always points from the past, which had lower entropy, to the future, which has higher entropy. When time has been slowed down by the gravity of a black hole entropy will be increasing at a slower rate, though from your perspective there will be no difference. The advanced progression of entropy will be written in the faces of your friends when you return, but from their perspective there has been no change of rate for anyone but you. But you might think that they sped up time by removing themselves to a region affected by a reduced gravitational field.
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