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 in Italy we neither meet with fragments of a supplanted nation, such as the Finns and Lapps in the Celto-Germanic domain and the black tribes in the Indian mountains; nor have any remains of an extinct primitive people been hitherto pointed out there, such as appear to be revealed in the peculiarly-formed skeletons, the places of assembling, and the burial mounds of what is called the stone-period of Germanic antiquity. Nothing has hitherto been brought to light to warrant the supposition that mankind existed in Italy at a period anterior to the knowledge of agriculture and of the smelting of the metals; and if the human race ever within the bounds of Italy really occupied the level of that primitive stage of culture which we are accustomed to call the savage state, every trace of such a fact has disappeared.
Individual tribes, or in other words, races or stocks, are the constituent elements of the earliest history. Among the stocks which in later times we meet with in Italy, the immigration of some, of the Greeks for instance, and the denationalization of others, such as the Bruttians and the inhabitants of the Sabine territory, are historically attested. Setting aside both these classes, there remain a number of stocks whose wanderings can no longer be traced by means of historical testimony, but only by a priori inference, and whose nationality cannot be shown to have undergone any radical change from external causes. To establish the national individuality of these is the first aim of our inquiry. In such an inquiry, had we nothing to fall back upon but the chaotic mass of names of tribes and the confusion of what professes to be historical tradition, the task might well be abandoned as hopeless.
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Reference address : https://www.ellopos.net/elpenor/rome/1-02-earliest-migrations-italy.asp?pg=2