Parallel universes.

time travel itself is pretty straightforward, isn't it?
according to einstein, time did not "travel" in a straight line, but instead moved like a spring. Each full rotation around the spring was about a full year. Now, also according to einstein, if you were to travel in time, you could only travel up and down the existing "spring". Therefore, you could not go back to the day before, but to that day exactly one year ago. Einstain stated this was because when the earth moves, it creates a gravitational field which modifies the time stream around it. So therefore time travel would occur differently on jupiter than on earth. if two men were to use time machine at the exact same time, but on on them on mars and one on earth, the man on earth would arrive at a different place in time than the one on mars. this is because both earth and mars have different gravitational fields that alter time accordingly. also, it would be very impossible to travel "forward" in time, as the spring has not yet reached that point in time yet. But you could however, instead be thrust into a dimension in which time travels faster (where earth has different gravitational field, altering time around it in a different manner) and then stay there until it is the desired "time" you wish to go to in your dimension.
The problem of this is that it would be very hard to accurately land on the spring in the place you want, and seeing as you are back in time, the spring has not "forged" itself to your time. Therefore, you could not yet exist. Also, you may or may not be able to even enter a faster dimension, leave alone leave one. Einstein realized thiese errors, and therefore left the aspect alone.

... It doesn't help me balance my checkbook.

... And it doesn't help to connect with other people in a framework of compassion and not indifference.

... So, what's your point?

Stay off the reefer