The principle of biennial intercalation is mentioned in one passage in
Herodotus (1. 32),^94 which means that Philadelphus could have been drawing
on some early Greek calendrical tradition. However, the record of intercala-
tions under Philadelphus is not sufficiently complete to confirm the consis-
tency or regularity of his intercalations; even if they occuron averagein
alternate years, this does not prove the existence of afixed biennial scheme.
The intercalary month is known to have varied under his successor Euergetes,
and the same cannot be ruled out in Philadelphus’reign; this alone would
undermine the theory that intercalation in their reigns followed afixed and
rigid scheme.^95
Samuel (1962) proposed, more boldly, that the months of the Ptolemaic
Macedonian calendar were set according to the Egyptian, 25-year cycle (i.e.
Parker’s cycle)^96 —which would imply a connection between the institution of
this cycle in Egypt and the arrival of the Ptolemies. According to Samuel,
double-dated papyri from the third centuryBCEconform exactly to Parker’s
25-year cycle, with the only exception that Macedonian dates were set one day
later. He explains this discrepancy as an attempt by the Ptolemies to retain the
Greek tradition of beginning the month atfirst visibility of the new moon,
rather than one day before, atfirst invisibility of the old moon. This theory,
however, has been demolished by Jones (1997) on the grounds that in one case
out of six, the Macedonian dates in double-dated documents occur not one but
two days after the date in Parker’s 25-year cycle (and according to Depuydt’s
1998 reading of Pap. Carlsberg 9, the incidence of two-day discrepancies may
be even higher).^97 This effectively proves that the Ptolemaic Macedonian
(^94) See discussion in Ch. 1 n. 110.
(^95) In the reign of Ptolemy II Philadelphus, only intercalary Peritios is attested; but under
Ptolemy III Euergetes (246– 221 BCE), attested intercalary months include Hyperberetaios, Peri-
tios, and Panemos (for the latest assessment of the evidence, see Bennett 2011). Samuel (1962)
75 – 6, (1972) 149 concluded that under Philadelphus the only intercalary month was Peritios, as
it was indeed the last month of the Macedonian year in Egypt, but that this rule was broken
under Euergetes. The record of intercalations, however, is insufficient to verify this conclusion.
(^96) Samuel (1962) 54–61; see also Bickerman (1968) 39–40, Grzybek (1990) 135–41.
(^97) Samuel was aware that some dates were discrepant from the 25-year cycle, and argued that
these were concentrated in the reign of Ptolemy III Euergetes, during which the calendar became
particularly disrupted (Samuel 1962: 75–106); but the theory of calendar disruption under
Euergetes is without good foundation (see now Bennett 2011). Grzybek (1990)passimattempts
to rescue Samuel’s theory by arguing that these irregularities result from some documents’
having been written at night, when according to the Macedonian calendar the next calendar
day would already have begun. This device has been used in other contexts to explain away one-
day calendrical discrepancies (e.g. in the Elephantine papyri: see Stern 2000a); but it implies that
legal documents were regularly written at night (and furthermore that this affected the way they
were dated), which is historically implausible ibid. Furthermore, the beginning of the day in the
Greek (and Macedonian) calendars remains a matter of controversy (Bowen and Goldstein 1994:
696 and nn.; Bennett loc. cit.).There is no need to rescue Samuel’s theory with far-fetched
explanations such as Grzybek’s; far more likely is that the 25-year cycle theory is simply
erroneous (see A. Jones 1997: 163–4).
156 Calendars in Antiquity