If it isn't a Friday or Saturday night and you want the achievement, unplug your internet cord or turn off your wireless connection to the Xbox so that you can play offline. Set your console's date to the next Friday or Saturday that is coming up, and set the time to 19:00 (7 PM). This can be done in Console Settings on the Dashboard, it is the very last panel on the same row where you can start up the game in your disc drive.
Now, play through any five episodes, just be sure that you finish them. As soon as the fifth episode is complete, the achievement will unlock. This obviously must be done locally, not only do you not have internet but the achievement states it must be single player. That means you can't play with anyone locally, either.
Have fun.
NOTE: You CANNOT get banned from Xbox LIVE for doing this. It is perfectly legal because it does not involve PC hacking tools, you have nothing to fear.