Temporal reasoning is captured in one manner by tense logic i.e. the logic of primitive tense-operators, and in another manner by the logic of instants (or dates) i.e. the earlier-later calculus. In terms of McTaggart's time-series we can say that tense logic is A-logical, whereas the logic of instants is B-logical. Thus we can speak about two kinds of temporal logic (A and B). This paper is based on a study of the relation between these kinds of temporal logic from a formal point of view.