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 Romans in Macedonia and Thrace
But this very conversion of Macedonia into a province directly dependent on Rome gave to the relations of Rome with the peoples on the north-east greater importance, by imposing on the Romans the obligation of defending the everywhere exposed frontier on the north and east against the adjacent barbarian tribes; and in a similar way not long afterwards (621) the acquisition by Rome of the Thracian Chersonese (peninsula of Gallipoli) previously belonging to the kingdom of the Attalids devolved on the Romans the obligation hitherto resting on the kings of Pergamus to protect the Greeks here against the Thracians.
From the double basis furnished by the valley of the Po and the province of Macedonia the Romans could now advance in earnest towards the region of the headwaters of the Rhine and towards the Danube, and possess themselves of the northern mountains at least so far as was requisite for the security of the lands to the south.
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Reference address : https://www.ellopos.net/elpenor/rome/4-05-peoples-north.asp?pg=14