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 this battle the Phoenician army no longer ventured to keep the field against the Romans; Alaesa, Centuripa, and the smaller Greek towns generally fell to the victors, and Hiero himself abandoned the Carthaginian side and made peace and alliance with the Romans (491). He pursued a judicious policy in joining the Romans as soon as it appeared that their interference in Sicily was in earnest, and while there was still time to purchase peace without cessions and sacrifices.
The intermediate states in Sicily, Syracuse and Messana, which were unable to follow out a policy of their own and had only the choice between Roman and Carthaginian hegemony, could not but at any rate prefer the former; because the Romans had very probably not as yet formed the design of conquering the island for themselves, but sought merely to prevent its being acquired by Carthage, and at all events Rome might be expected to substitute a more tolerable treatment and a due protection of commercial freedom for the tyrannizing and monopolizing system that Carthage pursued. Henceforth Hiero continued to be the most important, the steadiest, and the most esteemed ally of the Romans in the island.
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Reference address : https://www.ellopos.net/elpenor/rome/3-02-war-rome-carthage-sicily.asp?pg=16