The origins of the eight-year cycle are unclear, but its institution may have
come about in an unintentional manner. A sequence, indeed, does not become
a cycle until it is repeated. The fact that thefirst octaeteris began in 533/2 (or
527/6, or 525/4) does not mean that it was deliberately or even knowingly
instituted as a cycle in that year. The institution of the cycle could well have
been retrospective, when it was decided to repeat the sequence of the foregoing
eight years, or later still, after that the sequence had been inadvertently
repeated. It appears most likely that the initial attempt, under Cyrus, was to
institute a fixed pattern of intervals such as had been attempted under
Nabopolassar, although this time with greater precision. Instead of using a
constant interval (2½ years), an alternation of two intervals (2½ and 3 years)
was used. After a while, however, and at the latest at the beginning of the reign
of Darius, it was noticed that this alternate-interval scheme had produced an
eight-year cycle. Consequently, after the intercalation of 519/18, a choice
needed to be made: for if the next intercalation was to happen after a three-
year interval, as required by the alternation scheme, the eight-year cycle
pattern would have been broken. For some reason—perhaps awareness that
the alternate-interval scheme was not providing sufficient intercalation—the
eight-year cycle was preferred, and the next intercalation was made in 517/16,
2½ years later. In short, I am suggesting that the eight-year cycle gradually
evolved from an alternate-interval scheme. This would have represented, in
calendrical terms, a radical paradigm shift, since no cycle had ever been used
hitherto in the Babylonian calendar.
It is clear, nevertheless, that neither the alternate interval scheme, nor the
eight-year cycle, was sufficiently established or known in this period for
the intercalation to have been predictable. Intercalation was still subject to a
process of trial and error, and changes to existing patterns could have been
made at any time. This is why it was still necessary, at least under Cyrus and
Cambyses, for officials of the Esagila (the great temple of Babylon) to inform
the officials of the Eanna (its counterpart in Uruk) that certain months had
been made intercalary.^109 Nevertheless, we must regard the regularization of
intercalation from the beginning of Cyrus’reign as a profound, innovative,
and long-term change in the Babylonian calendar.
have been XII 2 , whereas it was VI 2 ). The same issue arises again with the 19-year cycle, and will
be discussed in detail below.
(^109) Parpola (1970–83) ii. 504 (from Clay 1919 nos. 15 and 196); see Parker and Dubberstein
(1956) 1,Wacholder andWeisberg (1971) 230. These texts may also suggest that the officials of
the Esagila were responsible, in some way, for the intercalation.
104 Calendars in Antiquity