The whole point of special/general relativity (at least the Minkowski approach to it, ie the approach that calls time a dimension) is that it the time dimension is related to the spatial dimensions. At non-relativistic speeds it seems unrelated, but for very fast-moving objects or particles the interplay between space and time becomes quite important, and for an object moving along a path the notions of time as-measured-by an external observer (roughly, ending coordinate in the time dimension minus the starting coordinate) and time as-measured-by the object (roughly, the Minkowski-length of a path in spacetime) become quite different things.