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
The consequences of this measure--which beyond doubt originated not in Philhellenism, but simply in the weakness and negligence of the Roman government-- were substantially similar to those which had occurred under the like circumstances in Greece; civil wars and usurpations so rent the land that, when a Roman officer of rank accidentally made his appearance there in 668, the inhabitants urgently besought him to regulate their affairs and to establish a permanent government among them.
In Syria also during the interval there had not been much change, and still less any improvement. During the twenty years' war of succession between the two half-brothers Antiochus Grypus (658) and Antiochus of Cyzicus(659), which after their death was inherited by their sons, the kingdom which was the object of contention became almost an empty name, inasmuch as the Cilician sea-kings, the Arab sheiks of the Syrian desert, the princes of the Jews, and the magistrates of the larger towns had ordinarily more to say than the wearers of the diadem. Meanwhile the Romans established themselves in western Cilicia, and the important Mesopotamia passed over definitively to the Parthians.
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Reference address : https://www.ellopos.net/elpenor/rome/4-08-east-king-mithradates.asp?pg=3