Time Traveler is add-on for Windows Home Server, which runs directly from WHS Console. Time Traveler allows a user to create roll-back points for changed files in any shared folder on home server. Through WHS console, users can roll-back a file or folder to any point in time. That means if you ever overwrite a file in your shared folders by accident, then you can simply restore it! Time Traveler for WHS is a commercial add-in, priced at $29.99/£19.25. A trial version is available which allows a maximum of 25 rollback points.
More info: Time Traveler for Windows Home Server