Right Ascension and defn of zero hour:-
http://en.wikipedia.org/wiki/Right_ascension
Why do you expect Polaris to be on the zero hour line? :-
http://seds.org/~spider/spider/Misc/alphaUMi.html
A bit more on the "Precession of the Equinoxes":-
http://www.astro.uiuc.edu/~kaler/celsph.html#equ
Here is the path of the NCP over 25,700 years:-
http://en.wikipedia.org/wiki/Imagerecession_N.gif