The calendar reforms of Peter the Great introduced on January 1, 1700 have produced a surprising amount of confusion and misunderstanding. This articles proposes firstly to clarify the aims and outcomes of these reforms, so far as the available sources allow. Secondly, through an examination of the New Year celebrations mandated by Peter's edicts, the article examines the legitimating arguments that have been deployed, including ideas about Russia's relation to western countries, about the position of the Orthodox Church in the polity, and about the prerogatives of the ruler in these matters. As a result of the changing arguments invoked by Peter and his entourage, the reforms introduced a regime of plural temporalities that has affected the course of Russia's development and the elaboration of its identities to this day. The reforms had little to do with heralding a secular, modern society. If initially they represented a failed pragmatic attempt to create a civil calendar aligned with Protestant countries, their justification, once it finally settled, harked back to long-standing theological ideas about the time of the Incarnation.