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
Accordingly the disputes as to the throne in Syria and in Egypt were referred for settlement to the Roman government. In the former after the death of Antiochus Epiphanes (590) Demetrius afterwards named Soter, the son of Seleucus IV, living as a hostage at Rome, and Antiochus Eupator, a minor, the son of the last king Antiochus Epiphanes, contended for the crown; in the latter Ptolemy Philometor (573-608), the elder of the two brothers who had reigned jointly since 584, had been driven from the country (590) by the younger Ptolemy Euergetes II or the Fat (d. 637), and had appeared in person at Rome to procure his restoration. Both affairs were arranged by the senate entirely through diplomatic agency, and substantially in accordance with Roman advantage.
In Syria Demetrius, who had the better title, was set aside, and Antiochus Eupator was recognized as king; while the guardianship of the royal boy was entrusted by the senate to the Roman senator Gnaeus Octavius, who, as was to be expected, governed thoroughly in the interest of Rome, reduced the war-marine and the army of elephants agreeably to the treaty of 565, and was in the fair way of completing the military ruin of the country. In Egypt not only was the restoration of Philometor accomplished, but--partly in order to put an end to the quarrel between the brothers, partly in order to weaken the still considerable power of Egypt--Cyrene was separated from that kingdom and assigned as a provision for Euergetes.
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Reference address : https://www.ellopos.net/elpenor/rome/4-01-gracchi.asp?pg=99