Interesting question. AFAIK, the Hebrew Calendar has a seven-day week based on the new moon. It was a lunar (or semi-lunar) calendar, as opposed to the pagan Julian calendar which did have an eight-day week. We celebrate Hanukkah for eight days because the oil–which was enough to last only one day–lasted for eight: thus the miracle. I look to someone with more knowledge to provide a better explanation concerning the calendars.
