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
Accordingly in the Italian languages short vowels are regularly dropped in the final sound, long ones frequently: the concluding consonants, on the other hand, have been tenaciously retained in the Latin and still more so in the Samnite; while the Umbrian drops even these. In connection with this we find that the middle voice has left but slight traces in the Italian languages, and a peculiar passive formed by the addition of -r takes its place; and further that the majority of the tenses are formed by composition with the roots -es and -fu, while the richer terminational system of the Greeks along with the augment enables them in great part to dispense with auxiliary verbs. While the Italian languages, like the Aeolic dialect, gave up the dual, they retained universally the ablative which the Greeks lost, and in great part also the locative. The rigorous logic of the Italians appears to have taken offence at the splitting of the idea of plurality into that of duality and of multitude; while they have continued with much precision to express the relations of words by inflections. A feature peculiarly Italian, and unknown even to the Sanscrit, is the mode of imparting a substantive character to the verb by gerunds and supines,--a process carried out more completely here than in any other language.
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Reference address : https://www.ellopos.net/elpenor/rome/1-02-earliest-migrations-italy.asp?pg=7