I do it every day; I mean time-travel. I'm so forgetful that I leave messages on my phone to give my future self a hint as to what surely was forgotten.
Then later, my past self faithfully provides instructions to my present self. I always wonder at the fact that my past self believes she's talking not to me, living in the moment, but to her future self.
Now that I've convinced you that you can time travel, I want to tell you that time travel is as old as mankind. If you put a narrow definition on time travel, you will belive you can't do it.
Those who used and taught the skills of time travel were called Shamans. A good book to illustrate these techniques is "Song of Heyoehkah" by Hyemeyohsts Storm. The book sweeps the reader away from life's cares and returns a person changed--maybe even changed for the better.