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 Tribes at the Sources of the Rhine and along the Danube - Helvetii - Boii - Taurisci - Cerni - Raeti, Euganei, Veneti
In these regions the most powerful nation at that time was the great Celtic people, which according to the native tradition(10) had issued from its settlements on the Western Ocean and poured itself about the same time into the valley of the Po on the south of the main chain of the Alps and into the regions on the Upper Rhine and on the Danube to the north of that chain.
10. Cf. II. IV. The Celts Assail the Etruscans in Northern Italy
Among their various tribes, both banks of the Upper Rhine were occupied by the powerful and rich Helvetii, who nowhere came into immediate contact with the Romans and so lived in peace and in treaty with them: at this time they seem to have stretched from the lake of Geneva to the river Main, and to have occupied the modern Switzerland, Suabia, and Franconia Adjacent to them dwelt the Boii, whose settlements were probably in the modern Bavaria and Bohemia.(11)
11. "The Helvetii dwelt," Tacitus says (Germ. 28), "between the Hercynian Forest (i. e. here probably the Rauhe Alp), the Rhine, and the Main; the Boii farther on." Posidonius also (ap. Strab. vii. 293) states that the Boii, at the time when they repulsed the Cimbri, inhabited the Hercynian Forest, i. e. the mountains from the Rauhe Alp to the Bohmerwald The circumstance that Caesar transplants them "beyond the Rhine" (B. G. i. 5) is by no means inconsistent with this, for, as he there speaks from the Helvetian point of view, he may very well mean the country to the north-east of the lake of Constance; which quite accords with the fact, that Strabo (vii. 292) describes the former Boian country as bordering on the lake of Constance, except that he is not quite accurate in naming along with them the Vindelici as dwelling by the lake of Constance, for the latter only established themselves there after the Boii had evacuated these districts.
From these seats of theirs the Boii were dispossessed by the Marcomani and other Germanic tribes even before the time of Posidonius, consequently before 650; detached portions of them in Caesar's time roamed about in Carinthia (B. G. i. 5), and came thence to the Helvetii and into western Gaul; another swarm found new settlements on the Plattensee, where it was annihilated by the Getae; but the district--the "Boian desert," as it was called--preserved the name of this the most harassed of all the Celtic peoples (Cf. III. VII. Colonizing of The Region South of The Po, note).
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Reference address : https://www.ellopos.net/elpenor/rome/4-05-peoples-north.asp?pg=15