« A.U.C. 813 = A.D. 60 »

The Pompeian graffito CIL IV 4182 states that Sunday a.d. VIII Id. Feb. A.U.C. 813 = 6 February A.D. 60, day 16 of a lunar month, was a market day in Cumae and 4 days before the Pompeian market day. The lunar date shows that the lunar month started on a.d. XI Kal. Feb. A.U.C. 813. 22 January A.D. 60 was a new moon. Thus the graffito confirms the alignment between the Julian calendar and the Roman calendar in the first century A.D.

Its greater importance is the data it provides for the behaviour of the Roman nundinal cycle. The related graffito CIL IV 8863 gives a cycle of market days at this time, which shows that the Roman market was two days after that at Cumae. If these two graffiti are combined, we may conclude that a.d. VI Id. Feb. A.U.C. 813 = 8 February A.D. 60 was a market day in Rome1. This is the only Roman market day that can be directly synchronised to an absolute Julian date.

If we could safely assume that the nundinal cycle was unbroken from that date back to Republican times, this result would fix the phase of the nundinal cycle in the Republic. However, Dio Cassius 60.24.7 notes that the market day was moved to another day in A.D. 44 due to "religious rites" and that the market day had been changed several times. Since markets were held in a series of towns on each day in the cycle, a change to the market day in one town would either require it to be swapped with that of another town or for the whole cycle to be delayed a day or more. Since there were several such circuits which intersected at the Roman market, the second alternative seems to be less disruptive. But either way such an event would have created a permanent phase shift.

It is possible to decide the cumulative total phase shift by A.D. 60, depending on the model of Republican chronology arrived at on other grounds. The distance between 1 January 45 and 8 February A.D. 60 is 38,024 = 8*4,753 days; thus, if there had been no break in the cycle, 1 January 45 should have been a market day. On the model preferred here, the nundinal letter for A.U.C. 709 = 45 was C, and Kal. Ian. A.U.C. 709 = 31 December 46. Hence the first market day in that year was 2 January 45 and the market cycle in 45 was 7 (mod 8) days out of phase with that of A.D. 60. On the standard model, the nundinal letter for A.U.C. 709 = 45 was still C, but Kal. Ian. A.U.C. 709 = 2 January 45. Hence the first market day in that year was 4 January 45; the market cycle in 45 was 5 (mod 8) days out of phase with that of A.D. 60.

P. Brind'Amour, Le calendrier romain 268ff. has argued that Pompeian graffito CIL IV 8863, refered to above, sheds some additional light on the question. This graffito gives (a) the days of the sabbatical week, starting with Saturday (b) a market circuit of 8 different towns, starting with Pompeii (c) an apparent countdown from a day X(VIII) to the Kalends of the next month, followed by NON, which is usually interpreted as a poorly written version of the name, and an apparently somewhat corrupt number of days in the next month up to the Ides, and (d) a count from I to XXX.

Brind'Amour suggests that the graffito is a ready reckoner for a lunar month in which day 1, a Pompeian market day, is equated to a Saturday, a.d. XIX Kal. of an uncertain 31-day month with an Ides on the 13th day. He concludes the month in question was either August or December. Assuming a lunar month based on conjunction, as in CIL IV 4182, the only date he found in the first century A.D. before the Vesuvian eruption of A.D. 79 that meets these conditions is Saturday 14 December A.D. 76. From CIL IV 4182, 10 February A.D. 60 was a market day in Pompeii. The distance between these two dates is 6,152 = 8*769 days. That is, the dates from the two graffiti imply that the nundinal cycle was stable between A.D. 60 and A.D. 76.

However, Brind'Amour's analysis is open to two objections:

  1. August and December are not the only 31-day months with an Ides on the 13th: there is also January. More significantly, CIL IV 4182 names 6 February A.D. 60 as a Sunday, but by modern reckoning it was a Wednesday. If CIL IV 8863 reflects a set of synchronisms for a specific date, the "Saturday" of CIL IV 8863 is unlikely to fall on a modern Saturday; by Brind'Amour's own explanation of this discrepancy, it should fall on a Tuesday. Extending Brind'Amour's search to include Tuesdays and Januarys, we find that CIL IV 8863 should actually fall on Tuesday 14 January A.D. 66. But the distance between this date and 10 February A.D. 60 is 2,165 = 269*8+5 days. If this is correct, the market cycle was retarded by five days in less than 6 years. This is very unlikely.

  2. The analysis depends on the assumption that CIL IV 8863 is actually a ready reckoner for a specific month. There are several reasons to doubt that this is so:

    1. As noted, the countdown in the Roman month is imperfect. The apparent name of the second month is given as NON. This has been assumed to be a badly written month name. According to Brind'Amour, Della Corte interpreted this NON as a badly written NOV(?); Degrassi as a very badly written IAN(??). The first can be ruled out since Id. Oct. was the 15th day of the month. The second interpretation is ruled out because the following entries read: VII, VI, V [...], but the day after Kal. Ian. is a.d. IV Non. Ian. There is no way to reconcile NON with a date in Septembri (Germanicus) or Februarius, which would be required if the month in question was Augustus or Ianuarius.

    2. The NON is followed by VII, VI, V [...] / NON VIIII VIII ... IDUS. The dates a.d. VII Non. and a.d. VIIII Id. do not exist, but the Nones is a.d. VIIII Id. in every month and the Kalends is a.d. VII Non. in Maius, Iulius and October. This might suggest we are looking for the 14th day in a 31 day month with an Ides on the 13th that was followed by a month with an Ides on the 15th. But there is no such month: Aprilis, Iunius and September are all 30 day months.

    3. It is, to say the least, a striking coincidence that all four cycles in the graffito start on the first day of the cycle: the first week day (Saturday); the first market day from a Pompeian perspective (Pompeii); the first day in which a month name is used (the day after the Ides of the previous month); and the first day of the lunar month.

    4. The 30 days of the lunar month are organised as two columns of 14 days and 2 extra days, a structure which clearly shows the relationship of the lunar month to the sabbatical week.

    To my mind it makes much more sense to interpret the graffito as a universal calendar, a compressed version of the annual fasti. The columns for the Roman month don't identify a particular month but show the generic structure of any month, which has up to 19 days before the Kalends, up to 7 days before the Nones (including the Kalends) and 9 days before the Ides (including the Nones), even though there is no single month with all these features. The NON after the Kalends is exactly what it appears to be: the Nones.

    Hence CIL IV 8863 cannot be used to identify a second imperial market day.

Dio vaguely explains that the nundinal cycle was interrupted in A.D. 44 "because of some religious rites". It is unclear what these were; indeed the wording suggests that Dio himself may not really have known. If indeed the market cycle was stable between A.D. 60 and A.D. 76, this would suggest that the adjustments made to the market cycle in and before A.D. 44 were somewhat arbitrary. Possibly Dio's remark that changes were made "at many other times" was directed specifically at Claudius, the subject of this particular chapter, and the changes were confined to his reign. But, if the delays were indeed introduced arbitrarily, it is probably impossible to reconstruct the history of the nundinal cycle in the early empire.

However, there is another possible solution. Surviving fasti do not show the leap day (the bissextile) and we have no statement of how it fitted into the market cycle. But Celsus 39, cited in Justinian, Digest 50.16.98, notes that a.d. VI Kal. Mart. and a.d. bis VI Kal. Mart. were treated as a single day with prior and posterior halves. If this fiction applied to the market cycle, so that the same nundinal letter was used throughout the year in both regular years and leap years, then the bissextile day was omitted from the nundinal cycle, with the effect that the cycle slipped by one day every four years against the Julian calendar.

Dio Cassius 48.33.4 shows that this rule did not apply in A.U.C. 713 = 41, since a leap day was inserted into that year so that Kal. Ian. A.U.C. 714 = 31 December 41 would not be a market day. This would not be possible under the proposed rule. But the same datum allows us to calculate the net phase shift between this market day and the market day of 8 February A.D. 60. On the standard model of the early Julian calendar, the market day fell on Kal. Ian. A.U.C. 714 = 1 January 40, 36,197 = 8*4,524+5 days before 8 February A.D. 60, giving a net phase slip of 5 days in the nundinal cycle. On the model of the early Julian calendar proposed here, the market day fell on prid. Kal. Ian. A.U.C. 714 = 30 December 41, 36,199 = 8*4,524+7 days before 8 February A.D. 60, giving a net phase slip of 7 days in the nundinal cycle.

If the nundinal cycle skipped the bissextile day but this was not part of Caesar's original reform, this rule was probably instituted as part of the Augustan reform of A.U.C. 746 = 8. Counting backwards from A.D. 60, there were 13 = 5 mod 8 bissextile days between the Augustan reform and CIL IV 4182 on the Scaligerian model, as required. On the model proposed here, there were either 14 = 6 mod 8 or 15 = 7 mod 8 bissextile days between the Augustan reform and the Pompeian graffito, depending on whether the reform was announced before or after the bissextile day of 8. Since we require 7 mod 8, we must conclude that the reform was announced before a.d. VI Kal. Mart. in A.U.C. 746 = 8, and that it did not cancel the bissextile day of that year but only the next three, resuming intercalation in the 12th year. But in either case this algorithm appears to explain the phase shift required.

There is however one extra twist. Every 8 years, including A.D. 44, the market was held on G days, the nundinal letter for a.d. VI Kal. Mart. This occurs on leap years, and a.d. VI Kal. Mart. is the date of the Regifugium. If the Regifugium was the first day of the biduum, the market might well be shifted by one day, to the bissextile day itself, to avoid a conflict with the Regifugium. Hence we can identify Dio's "religious rites" as the Regifugium.

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