I think we'd need to prove that telepathic messages can be sent in real time to someone in the next room before we try to prove that the messages can be sent over great distances and into the future and the past.
Proof that they can be sent realtime in the same room would be a good first step. glf5b's test where 1/3 of people told to go left instead go right fails to prove this. When I was in Army boot camp, 1/3 of recruits would turn right when the drill instructor ordered "Left-Face".