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
Beginning of the Maritime War - The Romans Build a Fleet
In fact, the Romans now for the first time felt the real difficulties of the war. If, as we are told, the Carthaginian diplomatists before the outbreak of hostilities warned the Romans not to push the matter to a breach, because against their will no Roman could even wash his hands in the sea, the threat was well founded. The Carthaginian fleet ruled the sea without a rival, and not only kept the coast towns of Sicily in due obedience and provided them with all necessaries, but also threatened a descent upon Italy, for which reason it was necessary in 492 to retain a consular army there.
No invasion on a large scale occurred; but smaller Carthaginian detachments landed on the Italian coasts and levied contributions on the allies of Rome, and what was worst of all, completely paralyzed the commerce of Rome and her allies. The continuance of such a course for even a short time would suffice entirely to ruin Caere, Ostia, Neapolis, Tarentum, and Syracuse, while the Carthaginians easily consoled themselves for the loss of the tribute of Sicily with the contributions which they levied and the rich prizes of their privateering. The Romans now learned, what Dionysius, Agathocles, and Pyrrhus had learned before, that it was as difficult to conquer the Carthaginians as it was easy to beat them in the field.
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Reference address : https://www.ellopos.net/elpenor/rome/3-02-war-rome-carthage-sicily.asp?pg=19