Currently you are sustained with you live in 3D.
That would mean up,down,left,right,forward,backward existing.
But time is also a dimension, that goes forward and backward.
You see, if you move in time you proportionally move in space. Let's say you are in a basement, and it's complete dark. You don't see anything, you don't feel anything or you are simply frozen, time still moves, and you actually still have motion. Your country is on the planet, the planet revolves around the sun so it moves. But the sun is also moving round the galaxy while the galaxy is existing in the universe.
What that means is that either you are not doing anything, you are in motion.
Same as for time. Even if nothing is alive, everything still moves. Futureward and pastward still exists with or without your content. Even if there's no entities (impossible) in the universe to have a 3D form, the time dimension form still exists for the simple fact that it does not depend on existence of anything except itself.