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
Through less frequented paths, and with a less favourable wind, a bolder mariner pursued a higher aim. Naevius not only like Ennius --although with far less success--adapted Greek tragedies for the Roman stage, but also attempted to create, independently of the Greeks, a grave national drama (-fabula praetextata-). No outward obstacles here stood in the way; he brought forward subjects both from Roman legend and from the contemporary history of the country on the stage of his native land. Such were his Nursing of Romulus and Remus or the Wolf, in which Amulius king of Alba appeared, and his -Clastidium-, which celebrated the victory of Marcellus over the Celts in 532. After his example, Ennius in his -Ambracia- described from personal observation the siege of that city by his patron Nobilior in 565.(50)
50. Cf. III. III. The Celts Conquered by Rome
But the number of these national dramas remained small, and that species of composition soon disappeared from the stage; the scanty legend and the colourless history of Rome were unable permanently to compete with the rich cycle of Greek legends. Respecting the poetic value of the pieces we have no longer the means of judging; but, if we may take account of the general poetical intention, there were in Roman literature few such strokes of genius as the creation of a Roman national drama.
Only the Greek tragedians of that earliest period which still felt itself nearer to the gods --only poets like Phrynichus and Aeschylus--had the courage to bring the great deeds which they had witnessed, and in which they had borne a part, on the stage by the side of those of legendary times; and here, if anywhere, we are enabled vividly to realize what the Punic wars were and how powerful was their effect, when we find a poet, who like Aeschylus had himself fought in the battles which he sang, introducing the kings and consuls of Rome upon that stage on which men had hitherto been accustomed to see none but gods and heroes.
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Reference address : https://www.ellopos.net/elpenor/rome/3-14-literature-art.asp?pg=76