This chapter compares different temporal regimes developed by the Seleucids and Ptolemies. Kosmin suggests that the Seleucids created a new “historical field” when Seleucus proclaimed a new epoch of Babylonian history and called the year of his conquest of Babylon year 1. The Babylonian historian and priest Berossus, despite writing a history of pre-Seleucid Babylonia, situated himself in the new world of the Seleucids. Yet in Egypt the Ptolemies continued reckoning with traditional regnal years, showing their subordination to traditional uses of historical time. But there were changes, too. Greek regnal years started with the anniversary of the king’s accession, oaths were sworn by the divinized royal members and Demotic dating formulae used the eponymous priests of the royal cult. All this established the Ptolemaic dynasty as a unit and a method of structuring time in its own way. Manetho and Berossus took over dynastic history, creating thirty dynasties up to the Macedonian conquest. The Ptolemies created a neue Zeit, but the Seleucids were more revolutionary. In both empires the local elites and populations participated in shaping the new politics of time.