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 when the Romans showed signs of attacking the Allobroges in their own territory, he offered his mediation, the rejection of which was followed by his taking the field with all his forces to help the Allobroges; whereas the Haedui embraced the side of the Romans. On receiving accounts of the rising of the Arverni, the Romans sent the consul of 633, Quintus Fabius Maximus, to meet in concert with Ahenobarbus the impending attack.
On the southern border of the canton of the Allobroges at the confluence of the Isere with the Rhone, on the 8th of August 633, the battle was fought which decided the mastery of southern Gaul. King Betuitus, when he saw the innumerable hosts of the dependent clans marching over to him on the bridge of boats thrown across the Rhone and the Romans who had not a third of their numbers forming in array against them, is said to have exclaimed that there were not enough of the latter to satisfy the dogs of the Celtic army.
Nevertheless Maximus, a grandson of the victor of Pydna, achieved a decisive victory, which, as the bridge of boats broke down under the mass of the fugitives, ended in the destruction of the greater part of the Arvernian army.
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Reference address : https://www.ellopos.net/elpenor/rome/4-05-peoples-north.asp?pg=6