Who used Year zero before him?
I told you, the French did, it being backdated to 1789. And he didn't 'use' it as such, except to make a not very good analogy, whereby instead of a victorious bourgeoisie, casting themselves as being representative of the whole population in destroying an arch-evil ancien regime, the Communist Party was in its place, as the country joined and caught up with the rest of the Communist-ruled world. In this analogy, the 1917 Bolshevik revolutionary model was superimposed upon the old French one.