That is the theme of NATA's open round: Discovering Time Travel
Make an animation based on this topic and you can participate in the open round! Just read over the rules and info first.
NATA is the Newgrounds Annual Tournament of Animation. It is run by Munchymedia, who created and previously ran TOFA.
Anyone can enter (tag your movie with "nata2012open") and the deadline for this round is May 10th!