This paper aims to provide an analysis, from a diachronic point of view, of the variation between que and ce que in the development of complex conjunctions in French. More particularly, we investigate temporal phrases, focusing on the necessity to take into account the source of the two structures: comparative correlation for que phrases, relative structures for ce que conjunctives. This difference allows us to explain that que phrases function as the unmarked case in the opposition, occurring in all sorts of contexts, while ce que phrases are used only in actualizing contexts.