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
But, after this boy had at length attained majority, the same senate showed utter passiveness towards his aggressions on all sides and towards the formation of this imposing power, the development of which occupies perhaps a period of twenty years. It was passive, while one of its dependent states became developed into a great military power, having at command more than a hundred thousand armed men; while the ruler of that state entered into the closest connection with the new great-king of the east, who was placed partly by his aid at the head of the states in the interior of Asia; while he annexed the neighbouring Asiatic kingdoms and principalities under pretexts which sounded almost like a mockery of the ill-informed and far-distant protecting power; while, in fine, he even established himself in Europe and ruled as king over the Tauric peninsula, and as lord-protector almost to the Macedono-Thracian frontier.
These circumstances indeed formed the subject of discussion in the senate; but when the illustrious corporation consoled itself in the affair of the Paphlagonian succession with the fact that Nicomedes appealed to his pseudo-Pylaemenes, it was evidently not so much deceived as grateful for any pretext which spared it from serious interference.
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Reference address : https://www.ellopos.net/elpenor/rome/4-08-east-king-mithradates.asp?pg=27