Is a time dimension possible

Can someone tell me how time is supposedly a dimension unto itself. I
understand the function of time as it is related to distance movent through
space as well as  change in state but change in state takes place at
different rates for different things and different systems. There are also
many different relationships in regards to distance or motion. How is it that
we can also be moving through a time dimension. Scientists are so quick to
say space-time and that they are seemingly integrated, but how can then there
also be time dimension. This implies a dimension which is distinct. It seems
that time is basically a function of state change , motion through space,
speed and distance. If there is a time dimension then where were any of us 5
minutes ago. 5 days ago, or 5 years ago. If a time dimension exists then we
should be able to discern where we were back in time and even go back in time
if we had the right technology. Since I was in a different state 5 years ago
how could I go back to that same state and since different things change
their state at different rates or speed then how would all these different
things reintegrate themselves to their previous state if they have no
internal knowledge of their previous state. If their is a specific time
dimension then the past should be kind of like a movie or hologram composed
of a complex array of electromagnetic energy patterns that describe how the
universe existed at any single moment in time. If this were true then our
whole universe would have to be viewed like a holographic computer program
and spacetime as the computer on which it runs. How would going back in time
be possible and how would you be able to go back and locate that array of
information that is locked up in time. Would there also be a spacetime energy
axis that you could somehow manipulate to go back to the desired set of
electromagnetic energy patterns in spacetime. If we did manage to get back
into time would our current electromagnetic energy patterns change
back(possibly through some repatterning mechanism) into their previous state
which would presumably be recorded into this array of EM information. Somehow
I am skeptical about a time dimension at this time and see time as a function
of state change in a system or as function of distance and speed but I will
keep an open mind. Maybe scientists who use this term spacetime should give
us better working definition of time and the time dimension as they think it
exists.