If, in Sein und Zeit, [Heidegger] thinks of time as "the transcendental horizon for any possible understanding of Being", this is not because Heidegger thinks truth is a function of historical trend. Rather Heidegger is thinking of time and history differently --not as either a flux or a succession of moments (or ages). but rather as concealments of Being itself. Time gives an understanding of Being (Sein) but Being itself, i.e. Seyn as Ereignis, gives time by giving it itself. There is time only by virtue of the granting of Beyng itself. History is of Beyng.