The expansion of the Universe happened?

longer ago than 13.5 billion years ago (give or take)? Isn't what we call the Big Bang essentially just what we can see? So at the edge of the observable universe, that is 13.5 billion light years away; but there is more stuff beyond that point that we cannot see. Wouldn't, then, the Big Bang have happened longer ago than 13.5 billion years ago? I am simply confused (not surprising, really); and I apologize for faulty logic (the New Year combined with a tad of stupidity will do that). Thank you for answering what I am sure is an incomplete question.