No one can tell the future, and even if you could, your knowledge of events would affect your actions, thereby changing the future you just told. My fave perpective on this was in Alan Moore's The Watchmen, the book, not that farcical motion picture.
Jon Osterman is doing his best to explain to Janey Slater after JFK got whacked that, though he could see the future, he could not really do anything about it because, to him, it was already happening. He told Laurie Juspeckzyc that everyone was a puppet, an he was just one that could see the strings. He couldn't do anything about the future, because the Osterman in the future's past didn't know what the Osterman in the present's past would know in the past's future.
Osterman: Soon you will tell me that you're sleeping with Dan Dreiburg.
Juspeckzyc: You mean, you know about me and Dan?
O: Not yet, but you will reveal it to me as we have our conversation.
J: ARGHHH!!!