... though I don't think direct manipulation of time will ever be possible.
What you think possible and what
is possible are two entirely different matters.
The possibility of time travel (re: GR) has been known since 1949.
Other scenarios have been found to permit travel into the past. For example, in 1974 Frank J. Tipler of Tulane University calculated that a massive, infinitely long cylinder spinning on its axis at near the speed of light could let astronauts visit their own past, again by dragging light around the cylinder into a loop. In 1991 J. Richard Gott of Princeton University predicted that cosmic strings--structures that cosmologists think were created in the early stages of the big bang--could produce similar results. But in the mid-1980s the most realistic scenario for a time machine emerged, based on the concept of a wormhole.
http://www.sciam.com/article.cfm?id=0004226A-F77D-1D4A-90...