Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Towards the end of 690 Pompeius in person arrived in Syria,(15) and remained there till the summer of the following year, resolutely interfering and regulating matters for the present and the future.
15. Pompeius spent the winter of 689-690 still in the neighbourhood of the Caspian Sea (Dio, xxxvii. 7). In 690 he first reduced the last strongholds still offering resistance in the kingdom of Pontus, and then moved slowly, regulating matters everywhere, towards the south. That the organization of Syria began in 690 is confirmed by the fact that the Syrian provincial era begins with this year, and by Cicero's statement respecting Commagene (Ad Q. fr. ii. 12, 2; comp. Dio, xxxvii. 7). During the winter of 690-691 Pompeius seems to have had his headquarters in Antioch (Joseph, xiv. 3, 1, 2, where the confusion has been rectified by Niese in the Hermes, xi. p. 471).
He sought to restore the kingdom to its state in the better times of the Seleucid rule; all usurped powers were set aside, the robber-chiefs were summoned to give up their castles, the Arab sheiks were again restricted to their desert domains, the affairs of the several communities were definitely regulated.
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Reference address : https://www.ellopos.net/elpenor/rome/5-04-pompeius-east.asp?pg=41