scattered Christian communities to reckon the same calendar, and in the
fourth century facilitated the enforcement of a single date of Easter.
In a certain sense, therefore, the principle of calendar unity that was
established for thefirst time at the Councils of Arles and Nicaea in the early
fourth century was the outcome of gradual developments that were occurring
already in third-century Christianity; but more importantly it responded to
radical political changes that transformed the Roman Empire in the wake of
Constantine’s reign and conversion to Christianity. For the prime mover of
these councils, as is well known, was Constantine himself, whose main con-
cern at Nicaea was arguably to complete the unification of the Roman Empire
following his conquest of the East in 324CE. This unification was to be political
as well as religious; the latter involved, on the same par, the eradication of the
‘Arian heresy’and the united observance of Easter. The eradication of calendar
diversity became essential, for Constantine, at once to the cohesion of the
Church and to the cohesion of the Empire. This provides us with another,final
example of how political rulers and political issues determined the formation
and development of calendars in Antiquity.
In broader terms still, the rise of thefixed, Orthodox Easter cycle, the
ultimate outcome of the Council of Nicaea, was the culmination of a macro-
historical pattern that characterized, as we have seen in this book, all the great
empires of Antiquity, whereflexible, empirical calendars gradually developed
intofixed, calculated schemes, and where fragmented diversity gave way to
calendar unity. For the Achaemenid kings and Julius Caesar, the adoption of
afixed, Egyptian-type calendar was only implicitly (if at all) driven by an
administrative need or an ideological policy of unifying, through a single time-
reckoning scheme, their wide-flung imperial territories. But Constantine, near
the end of Antiquity, was thefirst great imperial ruler to use the calendar,
explicitly and deliberately, for purposes of generating political unity. His
calendar policy was the culmination of a long process of imperial centraliza-
tion that had begun in the Near East a millennium earlier, and that had led to
an increasingly unitary conception of empire, religion, and society.
424 Calendars in Antiquity