between the equinox and the 19-year cycle; the equinox, therefore, does not
provide an astronomical rationale to the Babylonian 19-year cycle.^126
Furthermore, the odd construction of the Saros Canon cycle, with one
short, two-year interval and two sequences of two long, three-year intervals
(see Table 2.3) suggests very strongly that this cycle was not the intentional
design of any astronomer. A cycle designed by an astronomer would have
been given a far more rational pattern. The‘optimal’19-year cycle (see Table
2.3) would have been not only better balanced, but also the easiest and most
natural to construct fromfirst principles, as it consists very simply of an
alternation of 3 and 2½ year intervals—as was already followed during
Cyrus’and Cambyses’reigns—with an additional 2½ year interval at the
end. That this cycle was not used, so far as the evidence suggests, at any
stage in Babylonian history must be regarded as highly significant. It indicates
that the various intercalation cycles that were adopted, culminating with the
Saros Canon cycle in the later Achaemenid and Seleucid periods, were not the
result of scientific discoveries, but rather the result of a gradual, haphazard
in 373BCE(year 14 of the cycle) the equinox is said to have been on 2 Nisannu (which would have
30 March, whereas we know the true equinox was 4 or 5 days earlier). Britton (2007) 123 suggests
that the framers of the 19-year cycle must have had‘a more accurate idea of the date of the
equinox’than was later laid down by the Uruk scheme; but this is an unwarranted hypothesis.
There is no reason why anyone should assume that the equinox as we now reckon it would have
been of any significance to the Babylonians.
(^126) Britton (2007) 120–4 sees a progressive retardation of the Babylonian calendar between
the mid-8th and late 6th cc.BCE, such that at the beginning of this period Nisannu always began
before the equinox, whereas by the early 5th c.BCE, when the 19-year cycle was instituted,
Nisannu always began on or after it. He further interprets this progressive retardation (due, no
doubt, to a slight but consistent tendency to over-intercalate) as‘a gradual program of letting the
beginning of the year slide later in the seasonal year with the aim of restoring the ancient
calendaric tradition in which the equinox fell in...month XII’(as in the Old Babylonian
calendar, and not in month I as in the more recent, neo-Assyrian calendar). In thefirst half of
the 6th c. the process was accelerated, which suggests‘an effort to restore the calendar to the Old
Babylonian convention immediately rather than gradually’. However,‘that effort was quickly
countered by a reversion to a more gradual and less discontinuous path of change’; eventually,
this more conservative approach won out (ibid. 124). It seems most unlikely, however, that a
program of calendar reform should have been intentionally designed—as Britton argues—in
such a way as to be implemented over the very long period of about two centuries. This would
have meant that the reformers would never have lived to see the outcome of their reform,
and would have needed to rely on future generations to accept the terms of the reform and
understand it sufficiently well to carry it out effectively and accurately. Far more reliable and
expedient, instead, would have been to carry out a single supernumerary intercalation, which
would have shifted instantly the whole calendar into the desired (on this interpretation, Old
Babylonian) relation; this is how calendar reforms are normally implemented. The equinox is
therefore unlikely to have motivated the tendency to over-intercalate in the earlier period, or to
have determined the institution of afixed cycle (and hence, naturally, the arrest of this tendency)
in the 5th c.BCE.
118 Calendars in Antiquity