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
After the ignominious failure of the Attic expedition, Syracuse became so indisputably the first Greek maritime power that the men, who were there at the head of the state, aspired to the sovereignty of Sicily and Lower Italy, and of both the Italian seas; while on the other hand the Carthaginians, who saw their dominion in Sicily now seriously in danger, were on their part also obliged to make, and made, the subjugation of the Syracusans and the reduction of the whole island the aim of their policy.
We cannot here narrate the decline of the intermediate Sicilian states, and the increase of the Carthaginian power in the island, which were the immediate results of these struggles; we notice their effect only so far as Etruria is concerned. The new ruler of Syracuse, Dionysius (who reigned 348-387), inflicted on Etruria blows which were severely felt. The far-scheming king laid the foundation of his new colonial power especially in the sea to the east of Italy, the more northern waters of which now became, for the first time, subject to a Greek maritime power. About the year 367, Dionysius occupied and colonized the port of Lissus and island of Issa on the Illyrian coast, and the ports of Ancona, Numana, and Atria, on the coast of Italy.
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Reference address : https://www.ellopos.net/elpenor/rome/2-04-fall-etruscan-celts.asp?pg=6