Tabletop Tuesdays: Change History in an Hour or Less by costik
"Time travel would seem to be a fairly intractable subject for a game. After all, paradoxes are a major issue, and the sheer variety of potential outcomes are a challenge, at least if you posit that changing the time stream is at all feasible (and if you don't, then time travel is nothing more than historical tourism). That's one reason that Chrononauts is such a clever design; it tackles the problem head-on, producing something quite satisfying (and even instructional for younger players without much knowledge of history) with what is, when you come down to it, a remarkably simple and quite clever system."