Time is a dimension, like length. That mile of road ahead of you doesn't not exist until you reach it, does not only exist as you traverse it, and does not cease to exist after you passed over it. "Time" is a descriptor of something that exists, just like length is a descriptor of something that exists. Time does not have any independent existence - it describes a quality of something else. Time describes a perception of existence - it is not independent of it.

Its a reiteration of memory in space