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 Antiates indeed continued to prosecute their commerce with armed vessels and thus, as occasion offered, to practise the trade of piracy also, and the "Tyrrhene corsair" Postumius, whom Timoleon captured about 415, may certainly have been an Antiate; but the Antiates were scarcely to be reckoned among the naval powers of that period, and, had they been so, the fact must from the attitude of Antium towards Rome have been anything but an advantage to the latter.
The extent to which the Roman naval power had declined about the year 400 is shown by the plundering of the Latin coasts by a Greek, presumably a Sicilian, war fleet in 405, while at the same time Celtic hordes were traversing and devastating the Latin land.(7)
7. Cf. II. IV. Fruitlessness of the Celtic Victory
In the following year (406), and beyond doubt under the immediate impression produced by these serious events, the Roman community and the Phoenicians of Carthage, acting respectively for themselves and for their dependent allies, concluded a treaty of commerce and navigation-- the oldest Roman document of which the text has reached us, although only in a Greek translation.(8)
8. The grounds for assigning the document given in Polybius (iii. 22) not to 245, but to 406, are set forth in my Rom. Chronologie, p. 320 f. [translated in the Appendix to this volume].
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : https://www.ellopos.net/elpenor/rome/2-07-pyrrhus-rome-italy.asp?pg=56