Intercalation in the neo-Babylonian periodIn Table 2.1, I present the intercalated years ranging from the reign of
Nabopolassar (when our continuous record of intercalations begins) to the
fall of the neo-Babylonian dynasty and the accession of Cyrus, and the
intervals between intercalations. A cursory glance at this table suffices to
establish that throughout this period, there was no pattern of intercalations
or any repeated sequence of intervals between them. The erratic succession of
intercalations means that no cycle, such as the 19-year cycle, was employed.
Some important remarks, however, need to be made. At the beginning of
this table, there is an almost unbroken succession of 2½ year intervals between
intercalations in the period corresponding broadly to Nabopolassar’s reign
(625—604). This suggests a deliberate attempt, in this period, to institute a
fixed intercalation scheme. The recurrence of 2½-year intervals could not just
have been the result of a strict astronomical regulation of the intercalation
such as is described in MUL.APIN and other earlier sources (see above),
because this would not have yielded repeated identical intervals. Moreover,
the 2½-year scheme yields excessive intercalation, unlike stellar criteria such
as those in MUL.APIN which are reasonably accurate.^102 Thus it is clear that
the astronomical principles used earlier on by Assyrian astrologers (such as
Balasî, cited above) to regulate intercalation were being abandoned in favour
of afixed scheme. It may be conjectured that the adoption of this innovative
scheme was intended to signal Babylonia’s newly acquired independence,
under Nabopolassar, from the Assyrian kingdom (which eventually fell in
612 BCE). At the very least, the concurrence of this scheme with the reign of
Nabopolassar suggests that it was directly instigated by the king, who, as we
have seen, had traditionally been in charge of the process of intercalation.^103
The 2½-year scheme runs until the beginning of Nebuchadnezzar’s reign
(603/2, year 2 of his reign), after which it was abandoned and the sequence of
intercalations became, it seems, completely erratic. Intervals between inter-
calations, however, were never less than 2 or more than 3½ years. The only
exception occurred towards the end of Nebuchadnezzar’s reign, in 569/8–563/
2, with a 4½-year interval followed by an obviously corrective 1½-year interval
(the latter still in Nebuchadnezzar’s reign). The reason for this aberration
is unknown, but political factors might be considered: calendrical disruption
was possibly caused, somehow, by Nebuchadnezzar’s failed campaign in Egypt
in 567.
(^102) Intercalations at regular intervals of 2½ years amount to 8 intercalations in 20 years,
significantly more than the optimal relation of 7 intercalations in 19 years. The only three-year
interval, towards the end of Nabopolassar’s reign (in 608/7), may have constituted an attempt to
correct this inaccuracy by exceptionally delaying the intercalation by six months. 103
See also below, n. 106.
100 Calendars in Antiquity