I have always thought of time as being no future or past, but an always moving present which has inertia. If you consider 1st dimension being left-right, 2nd dimension as being left-right and up-down, then 3rd dimension as left-right up-down and back-forth, then the 4th dimension would be left-right up-down back-forth forward in time-back in time. In the 1st dimension, with that explanation, the always moving variable as I mentioned time as being in the first sentence (remember that there is time movement in the 4th dimension) would be the up-down motion. In the 2nd dimension, this is the back-forth motion. "Time" to the 2nd dimension beings is moving back and forth. Under this explanation that I thought of while tripping on a few hundred mg of dxm, 2nd dimension beings would constantly be moving at a fixed rate, back and forth. The same goes for the up-down motion for 1st dimension forms. For the 3rd dimension (us), time is moving at a fixed rate and therefore, for the 4th dimension people, there is free and willing movement throughout time. However, the really trippy question is: what is the fixed rate variable for the 4th dimension forms?