Dating formulas abound in Roman Egypt. One could, for example, name the acting consuls to identify the year, or count the regnal year of the reigning emperor(s). Eras, that is a continuous count of years from a significant moment, were late-comers in Egypt. The common era, which counts the years since the birth of Christ, was an invention of the sixth century, and took several centuries to spread. In the fourth century CE, however, another, remarkable era appears in Egyptian documents from the city Oxyrhynchus, which consists not of one year count, but, e.g. year ρπθ ρνη = 189/158. This is quite practical. Instead of writing down entire names, a few numerals suffice to pinpoint exactly which circle around the sun is meant by the author. This comes in very handy when one orders a delivery of wine, or when one sends a very short note to a servant. And when one year is badly legible, the other number will bring clarity. But where does this dating formula come from?
According to Roger Bagnall and Klaas Worp (Chronological Systems of Byzantine Egypt, 2004: 55-58), who in turn refer to the early twentieth-century scholars Preisigke, Grenfell, and Hunt, the formula, in the static form we encounter it from the fourth to sixth century, is based on continued use of the regnal years of Constantius II (324-361) and Julian (355 – 363). Julian was Constantius’ cousin, whom he co-opted as (junior) co-emperor to manage the enormous Roman Empire. The ‘real’ first year of Era of Oxyrhynchus would then be, according to Bagnall and Worp, 40/9 (cf. P. Oxy. 63.4373), that is: 363-364 AD – the year in which Julian’s reign ended and the decision to nevertheless continue to count his regnal years was taken. For the attentive reader: that they continued to count Constantius’ years after his death in 361 is not taken as significant, as they did the same with the regnal years of his father Constantine the Great, who had likewise made his sons co-emperor. But this lasted only briefly, whereas the count of the regnal years of Constantius II and Julian was continued for centuries.
At first sight, the choice for Constantius II and Julian II is an odd one in the Later Roman Empire, in which Nicene Christianity eventually turned out to be the dominant religion. Constantius II was an Arian (a form of Christianity that got the label of ‘herecy’). Julian is often nicknamed ‘the Apostate’ because he swore off Christianity altogether. People could have opted to restart counting with the regnal years of new emperors, as they had done before. Is there some secret message behind the use of Julian’s regnal years? Did it start out as a declaration of loyalty from Oxyrhynchite crypto-pagans to the last pagan emperor? Or were people in Oxyrhynchus simply tired of keeping up with who was emperor at which point in time?
Let us take a look at the ‘political option’. How conscious are we, today, of the exact meaning of our dating formulas? It is not likely a lot of people – in the Netherlands, at least – think of baby Jesus when they write down the present year, even though there is no Dutch equivalent for ‘Common Era’ and dating things in temporal distance to the birth of Christ is still very much in use, especially when someone is talking about something before the year 1 AD. Even though most people know the medieval monk who calculated the birth of Christ probably was four years off, everyone sticks to 1 as a point of reference for BC and AD. It seems to be a matter of convenience, certainly when 1 forms the divide between the secular BCE and CE. People who employ the Anno Mundi (3761 BC(E)) or Hegira (622 AD/CE) in a country that in majority uses ‘1 AD’ appear to make a more conscious, religiously motivated choice – to give examples of non-convenience motivated choices.
So, is there a secret message behind using the unending reigns of Constantius II and Julian II as dating formula on short notes from Oxyrhynchus? There sure was not at the beginning of the sixth century, in 513 AD. When on P. Oxy. 16.2005 Ioannes, a village elder of Sephta, acknowledges he has received money for the repair of a wall, he adds a (Christian) cross to the note he dates with the reigns of Constantius and Julian and starts the summary on the back of the note with a chi-rho. Ioannes seems to have been consciously Christian and unknowingly using the reign of the last pagan emperor to date his little note. Ioannes might not have been aware of the origin of his dating formula. Were people in the centuries before him?
Most of the documents we possess are fairly neutral. A shipmaster declared he had received a certain amount of grain in 371 (P. Oxy. 48.3395) and Nikon paid his debt in 391 (P. Oxy. 72.4897). In 392, the Oxyrhynchus Era was used to describe the start of a period in which Apollonia, a perfume-seller, had to pay a certain amount of money on a daily basis to Syrion, master of the guild of perfume-sellers (P. Oxy. 75.5064). The only ‘political receipt’ we find comes from 362, a time in which Julian was still alive. On the back of an order to pay dated by the reigns of Constantius II and Julian II, someone had felt obliged to write down a confession of his faith: ‘There is one god’ (P. Oxy. 7.1056). The contents of the receipt have nothing to do with Julian, so we cannot conclude this profession of faith was somehow anti-Julian. What we do find, is the fact that using his regnal years for dating e.g. the reception of grain has survived his damnatio memoriae.
Oxyrhynchus seems to have been the only Egyptian city to have used the reigns of Constantius II and Julian II for their ‘Era’. Was the choice efficiency-driven? Starting anew after the death of every emperor, might, eventually, cause confusion. What if the same combination of numbers occurs twice, e.g. 40/9? All in all, the most probable explanation is that people in Oxyrhynchus decided to keep on counting the years of Constantius and Julian this makes business a lot easier. If, hypothetically, a contract has a duration of four years, one would not have to convert the dates to the new system of regnal years in case both emperors died during the four years agreed upon in the contract. The main reason for sticking to two (controversial) emperors appears to have been a matter of efficiency, nothing more. The orders of wine and other short receipts (with and without crosses) dated in years of the Oxyrhynchus Era probably are not very political. Optimalisation of business operations is likely to have been a goal of government officials, household servants and entrepreneurs alike. More detailed research into the use of this dating formula will have to establish whether this suspicion is correct.