This depends on which calendar is being used. No, I think I understand the Q & have rearranged it: the years 0-99 are not the 0 century, they are the 1st century. In the same way 1900s becomes...
Century is a time period of 100 years (stemming from the Latin cent meaning 100).Centuary is of or pertaining to Centaurs the mythical creatures (half man, half horse).