Another reason why we celebrate 8 days.
It says the Yevonim tried to snuff out the jewish flame, for good, by taking away 3 central things: shabbos, rosh chodesh and milah.
shabbos is the central and principal testimony to being Jewish.
rosh chodesh is the basic time period which makes up the Jewish calendar for us to live and celebrate our national celebrations/yom tovim. And milah is the bris between Hashem and a yid.
The Yom Tov of Chanukah celebrates these 3 areas of yiddishkeit.
1) Chanukah always has a shabbos
2) Chanuka was established on 25th of Kislev so that there will always be a Rosh Chodesh