I've read of how Nostradamus went forward in time to predict the end of the world and a lot of other events that have come true.
He apparently used the 'practices' used by ancient Egyptians to travel to the future. Perhaps this could apply to going back to the past.
Some one I know recommended a 'past lives' course she wanted to do so much, I gave it a go but never saw anything.
Perhaps its an individual thing to be able to go back to the past or forward to the future.