to akshually your actually post, the 12 IS zero. noon, as in midday isn't zero, which is a sort of arbitrary decision. That's the differentiating feature between the two systems.

Technically i guess you could count the noon point as 0 also, but that provides ambiguity, so i think it;s better to treat noon as 12, and midnight as 00:00 (but listed as noon) because then it perfectly maps to 24hr time.