do you realize this is even far easier than that!
every packet of info on the net has a time to live signature.
if someone were to ring routers and dedicated cable around the world, and special packet life span, conventional science tells us the "packet" when traveling at the speed of light will either lead or lag time based upon the direction in relation to the rotation of the earth. So you could in all probability send yourself an email to get milk yesterday
(yes and this is from the think tank...booze and brains are just tooo scarey