Time Paradox

Whitney and I just finished the Back to the Future trilogy (thanks Wendy and Jacob). I forgot how progressively worse those movies got. But is was nice to finally get more of the 80's references since I was too young when they came out. In the second one, however, there is a time paradox that I would like for someone to explain to me. Old man Biff hi-jacks the time machine to give the almanac to young Biff and then returne to the same future he had left. When Doc and Marty (a couple?) realize this, Doc says they can't go back to the future (doh!) because it would now be a totally different one. Hello?! Then how the heck did Biff do it. Am I to believe that Biff has more experience and knowledge of time travel? Maybe he just pushed the button in the car that said "return to original location and dimension". So I throw this question to you the reader to answer. Note: Anybody trying to answer this question seriously will look like an idiot or a communist.