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 Roman literature is the only one as to which we can still form an opinion; and, however problematical its absolute worth may appear to the aesthetic judge, for those who wish to apprehend the history of Rome it remains of unique value as the mirror of the inner mental life of Italy in that sixth century--full of the din of arms and pregnant for the future--during which its distinctively Italian phase closed, and the land began to enter into the broader career of ancient civilization. In it too there prevailed that antagonism, which everywhere during this epoch pervaded the life of the nation and characterized the age of transition.
No one of unprejudiced mind, and who is not misled by the venerable rust of two thousand years, can be deceived as to the defectiveness of the Hellenistico-Roman literature. Roman literature by the side of that of Greece resembles a German orangery by the side of a grove of Sicilian orange-trees; both may give us pleasure, but it is impossible even to conceive them as parallel. This holds true of the literature in the mother-tongue of the Latins still more decidedly, if possible, than of the Roman literature in a foreign tongue; to a very great extent the former was not the work of Romans at all, but of foreigners, of half-Greeks, Celts, and ere long even Africans, whose knowledge of Latin was only acquired by study. Among those who in this age came before the public as poets, none, as we have already said, can be shown to have been persons of rank; and not only so, but none can be shown to have been natives of Latium proper.
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Reference address : https://www.ellopos.net/elpenor/rome/3-14-literature-art.asp?pg=109