I was working today (00 Dec, 0000) on an experiment to send messages to a space-time co-ordinate in the past. If this experiment is successful I should receive this mail on 00 Feb, 0000, a date in the past.  It is quite funny that we can remember the past but not the future.  So, when I receive this message on (00 Feb, 0000), I wouldn't remember that this is the result of a successful revolutionary experiment to be performed in future. I should have got this message time stamped by a trusted time stamping authority in order to prove that this message is indeed from the future but that has its own problems. Why would I, in the past, believe that such a trusted time stamping authority would exist in the future?  Moreover, I don't have time to get all this done as the world is coming to an end today. 