  McTaggart distinguished two ways of ordering events or positions in time. First, they might be ordered by the relation of earlier than. This ordering gives us a series, which McTaggart calls the B-series. A second ordering is imposed by designating some moment within the B-series as the present moment. This second ordering gives us a series that McTaggart calls the A-series. According to McTaggart, in order for time to be real both series must exist, although McTaggart holds that, in some sense, the A-series is more fundamental than the B-series. 