The date of the Periplus can be determined by the political and geographical information offered by its author. The Periplus mentions the Nabataean King Malichus II who was in power from AD 40 to AD70.132 The author also describes how the Saka Kingdom in western India was ruled by a warlord named ‘Manbanos’, who must be King Nahapana because of the phonic similarity and the match of dates. Indian coins and inscriptions confirm that Nahapana held power in northwest India during the mid-first century AD.133
The Periplus describes how the Sakas seized territories on the Konkan seaboard from the Satavahana realm. Inscriptions from an Indian holy site called Nasik confirm that the Sakas held the territory for several years, during which time they offered royal gifts to Hindu shrines that were commemorated in dedicatory inscriptions. These inscriptions offer dates based on a royal calendar that counted from about AD 10. This was the year when the last Indo-Scythian kings lost power in the Indus region and the Saka regime in Gujurat became an independent realm. Saka inscriptions at Nasik dated from ‘year 41’ to ‘year 46’ were probably set up between AD 51 and AD 56. The Periplus must date to this short period before the Satavahanas reclaimed their former territories, which included Nasik.
There is also the issue of Sri Lanka which is described in the Periplus as a vast unexplored island beyond the scope of regular Roman trade voyages. Roman merchants speculated that Sri Lanka and Madagascar might be part of the same enormous island. The Periplus reports that in Sri Lanka ‘only the northern regions are civilised’ and the island ‘extends almost to the part of Azania (East Africa) that lies opposite’.134 This viewpoint must pre-date the reception of a Sri Lankan embassy in Rome by the Emperor Claudius (AD 41-54).
The Periplus was probably amongst a collection of trade reports assembled by the governor of Egypt when Sinhalese ambassadors arrived in his province (AD 52). The reports were copied and sent to Rome with the ambassadors so that central government could appraise the possible significance of Sri Lanka and the scope of eastern trade. Some of these reports entered imperial archives and were later read by Pliny the Elder who cites Indian Ocean sailing times dated to this period. Pliny reports that Roman ships left for India on ‘the sixth day of the Egyptian month Mechir, just before January the thirteenth in our calendar’.135
The two calendars were misaligned, so these dates only coincided in the four years between AD 48 and AD 52.136 The surviving Periplus was probably archived in Alexandria where it was transferred into Byzantine State records in late antiquity. The Periplus is the only document of its kind to survive and it therefore offers modern scholars a unique insight into the scope and significance of international maritime commerce in ancient times.