The Bosporan era (BE or AB), also called the Bithynian era, Pontic era or Bithyno-Pontic era, was a calendar era (year numbering) used from 149 BC at the latest until at least AD 497 in Asia Minor and the Black Sea region. It originated in the Bithynian Kingdom and was also used in the

Pontic Kingdom Pontus ( grc-gre, Πόντος ) was a Hellenistic kingdom centered in the historical region of Pontus and ruled by the Mithridatic dynasty (of Persian origin), which possibly may have been directly related to Darius the Great of the Achaemenid ...

and, for the longest time, in the Bosporan Kingdom. The calendar era begins with the assumption of the royal title by Zipoetes I of Bithynia in October 297 BC (in the Gregorian calendar), which marks the start of its year one.Jakob Munk Højte, "From Kingdom to Province: Reshaping Pontos after the Fall of Mithridates VI", in Tønnes Bekker-Nielsen (ed.), ''Rome and the Black Sea Region: Domination, Romanisation, Resistance'' (Aarhus University Press, 2006), 15–30. The Bosporan year began at the autumnal equinox. The earliest evidence for the use of the Bithynian era is some coins dating from 149/8 BC, when Nicomedes II overthrew his father, Prusias II. Since earlier Bithynian coins carry no date, it is possible that the calendar was invented on this occasion. The era was adopted in Pontus under Mithridates VI, who introduced it onto the

Pontic coinage Pontic coinage probably began during reign of Mithridates II of Pontus. Early Pontic coinage imitated coinage with Alexander the Great's portraits. Later coinage is well known for its high decree of realism in portraits of the Pontic kings who wer ...

sometime before 96/95 BC, replacing the Seleucid era used up to then. Since Pontus and Bithynia were rivals at the time, the most likely date for the introduction of the Bithynian era into Pontus was during the brief alliance between the two countries during the invasion of Paphlagonia in 108 BC. The Bithyno-Pontic era fell out of use in northern Asia Minor following the Roman conquest in 63 BC. There is no evidence that it was suppressed by Roman authorities. Rather, the local authorities preferred to adopt new eras commemorating their joining the Roman province of Bithynia et Pontus. The province thus had several dating systems in use, including the Seleucid era, but the Bithyno-Pontic era was not among them. There is no evidence from Asia Minor of the Bithyno-Pontic era ever being used on anything other than coins. Inscriptions, however, survive from the northern shore of the Black Sea, the region that fell under the Bosporan Kingdom in the first four centuries AD. In the Bosporus, the era was used in conjunction with the months of the

Macedonian calendar The Ancient Macedonian calendar is a lunisolar calendar that was in use in ancient Macedon in the It consisted of 12 synodic lunar months (i.e. 354 days per year), which needed intercalary months to stay in step with the seasons. By th ...

. The first Bosporan coins bearing the era are from the reign of Mithridates VI's son,

Pharnaces II Pharnaces II of Pontus ( grc-gre, Φαρνάκης; about 97–47 BC) was the king of the Bosporan Kingdom and Kingdom of Pontus until his death. He was a monarch of Persian and Greek ancestry. He was the youngest child born to King Mithridat ...

, who never controlled Pontus and whose kingdom was thus restricted to the Cimmerian Bosporus. His coins were minted in Bosporus, but were of the Pontic type. The first distinctly Bosporan coins, which bear Bosporan era dates, are from 281 BE (17/16 BC) and were issued by Queen

Dynamis Dunamis (Ancient Greek: δύναμις) is a Greek philosophical concept meaning "power", "potential" or "ability", and is central to the Aristotelian idea of ''potentiality and actuality''. Dunamis or Dynamis may also refer to: * Dynamis (Bosp ...

. The earliest inscription dated with the Bosporan era can be read either 325 BE (AD 29) or else 313 (17) and mentions the reigning king,

Aspurgus Tiberius Julius Aspurgus Philoromaios ( el, Τιβέριος Ἰούλιος Ἀσποῦργoς Φιλορωμαῖος, fl. second half of 1st century BC and first half of 1st century AD; died 37/38) was a prince and Roman client king of the Bos ...

. While the Bosporan series of coins ends with

Rhescuporis VI Rhescuporis VI ( el, Τιβέριος Ἰούλιος Ῥησκούπορις, translit=Tiberios Ioulios Rheskoúporis), also transliterated as Rheskuporis or Rheskouporis and sometimes known as Rhescuporis the Last, is the last well-known king of ...

in AD 341, the latest inscription is from 794 BE (AD 497/8).

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