My friend Jono and I love films about time travel, partly because we love to untangle the plots and problems. Although the Fermi paradox would seem to rule out returning to the past. (If there was time travel we'd know about it now because they would have got around all the obstacles and returned in time.) Further compound by the problem of autoinfanticide. (However traveling to the future might be another kettle of fish.) So these are in no particular order my five favorite time travel movies.
Twelve Monkeys is also post-apocalyptic! Deja Vu is a wonderful date movie as it blends action with some tasteful romance. I still don't understand Donnie Darko, it's not a movie for the faint hearted. Primer is amazing in that it will actually, for an hour, allow you to travel through time! Terminator probably only just made the list because time travel while integral to the plot is explored to the full depth as the others. All the films have very little s-x, but all of them except Primer are fairly violent.