Unfortunately, if you didn't pause your game, I don't think there's much you can do. You can try to back it up by keeping the game closed, and replacing the appropriate game file, but I believe that the game will take the additional time into effect and your end results will be the same, but it won't hurt to try.

Also, it would help to know if the backup files you have are the ones automatically created by the game, or ones you made yourself. This could be an important factor on whether or not the game can be restored to a previous state.