to 517/16 (see Table 2.2), but inasmuch as it was not repeated, it was
presumably not intended as a cycle. Its fortuitous occurrence is only the result
of the regularity of intercalation in the early Achaemenid period.
It is important to stress that the 19-year cycle has no natural starting-point
(or‘epoch’). The Saros Canon cycle could equally be expressed starting from
another epoch, e.g. (as often assumed in modern scholarship): 2½– 3 – 3 – 2 – 3 –
3 – 2½, with the same sequence, but starting one intercalation earlier. Thus
although I have assumed, in my tables, the sequence laid out above and I have
numbered the years of the cycle accordingly from 1 to 19, it must be remem-
bered that my numbering is arbitrary.^111
In Table 2.4, I present the sequence of intercalations attested from the reigns
of Darius I, Xerxes, and Artaxerxes I, with a view to establishing to what extent
the Saros Canon cycle may have been already in use. I also consider the
possibility of a‘loose 19-year cycle’in which intercalations occur infixed
years (the same years as in the rigid, Saros Canon cycle), but the intercalary
month (VI 2 or XII 2 ) in each of these years can vary (similarly to the eight-year
cycle that might have been used under Cyrus and Cambyses, as I have
suggested above). The possibility of a loose cycle has not been considered by
previous scholars, because of an unspoken assumption that in a 19-year cycle,
the intercalary months arefixed and cannot be altered. This assumption is
unreasonable. There is evidence, indeed, that the question of which month to
be intercalary (VI 2 or XII 2 ) was regarded as secondary to the question of
whether the year should be intercalated. In a letter to the Assyrian king (cited
Table 2.3.The Saros Canon and the optimal 19-year cycles
Year Saros Canon 19-year cycle Optimal 19-year cycle
Intercalation
(month number)Interval from previous intercalation
(number of years)Intercalation Interval3 XII 2 3 XII 2 3
6 XII 2 3VI 2 2½
8 XII 2 2VI 2 3
11 XII 2 3 XII 2 2½
14 XII 2 3 XII 2 3
17 VI 2 2½ VI 2 2½
19 XII 2 2½ XII 2 2½
Source. The Saros Canon text is in BM 34597 (LBAT 1428)
(^111) Hartner (1979) 2–3 treats my year 17 as the epoch of the cycle, and so implicitly Britton
(1993) 67–8, largely following Neugebauer (1955) i. 33 n. 2, ii. 442–3, who infers from a list of
twenty intercalated years starting in 170SE(142/1BCE) that year 1 of the Saros Canon cycle must
have been the year of the intercalation of VI 2. This single text, however, hardly serves as evidence:
its starting-point in 170SEmay well be incidental. There is no evidence, in fact, as to how the
Babylonians themselves conceptualized this cycle.
106 Calendars in Antiquity