If you can travel to your future, it's predestination and you have no free will.
Travel to the past and it's in past tense since you have, by definition, already done it.
In the multiverse where there is free will, the timeline branches as each choice is made. If you go back and change something then your create a new future, a branch, but you have to remain in the branch you started from because there is another you in that new branch.
These aren't my rules for time travel, they are Jim's, fed to you by Bob and Vadderung. However Bob abuses the truth when he speaks, so be careful.
As usual YMMV.