Our present calendar, which takes the birth of Christ as the turning-point from which to count time both backward and forward, was introduced at the end of the eighteenth century. The textbooks present the reform as prompted by scholarly needs to facilitate the dating of events in ancient history without having to refer to a maze of different time reckonings. Hegel, as far as I know the only philosopher to ponder sudden remarkable change, saw in it a clear sign of a truly Christian chronology because the birth of Christ now became the turning-point of world history. It seems more significant that in the new scheme we can count backward and forward in such a way that the past reaches back into an infinite past and the future likewise stretches out into an infinite future. This twofold infinity eliminates all notions of beginning and end, establishing mankind as it were, in a potentially sempiternal reality on earth. Needless to add that nothing could be more alien to Christian thought than the notion of an earthly immortality of mankind and its world.
–Hannah Arendt, “Willing” (footnote), The Life of the Mind