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 these Transpadane Celtic districts were allowed to retain their existence and their national constitution--so that they formed not town-domains, but tribal cantons--and no tribute, as it would seem, was imposed on them. They were intended to serve as a bulwark for the Roman settlements south of the Po, and to ward off from Italy the incursions of the migratory northern tribes and the aggressions of the predatory inhabitants of the Alps, who were wont to make regular razzias in these districts.
The process of Latinizing, moreover, made rapid progress in these regions; the Celtic nationality was evidently far from able to oppose such resistance as the more civilized nations of Sabellians and Etruscans. The celebrated Latin comic poet Statius Caecilius, who died in 586, was a manumitted Insubrian; and Polybius, who visited these districts towards the close of the sixth century, affirms, not perhaps without some exaggeration, that in that quarter only a few villages among the Alps remained Celtic. The Veneti, on the other hand, appear to have retained their nationality longer.
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Reference address : https://www.ellopos.net/elpenor/rome/3-07-peace-hannibal-third-period.asp?pg=3