The topic to be addressed in this paper, that is, the distinction between the “concept” of time and the being of the clock, divides into two parts: first, in the debate between Albert Einstein and Henri Bergson, one discovers the ground for the diverging concepts of time characterized by physics in its opposing itself to philosophy. Bergson’s durée or “duration” in opposition to Einstein’s ‘physicist’s time’ as ‘public time,’ one can argue, sets the terms for Martin Heidegger’s extending, his ontological (...) analysis of Da-sein, as human being-in-the-world. Second, in this the ‘concept of time’ gives way to the analysis of the ‘being of the clock.’ What is this being of the clock that makes evident the fundamental temporality of Da-sein? This question is rehearsed in Division Two of Being and Time. My claim is that the fundamental insight into the nature of time revealed by the encounter between Bergson and Einstein is that time extemporizes itself. Temporality “is” not a being but a process that temporalizes itself, precisely because it “is not.”. (shrink)