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
But, after Philopator's death (549), the right moment for crushing Egypt appeared to have arrived; with that view Antiochus entered into concert with Philip, and had thrown himself upon Coele-Syria, while Philip attacked the cities of Asia Minor. When the Romans interposed in that quarter, it seemed for a moment as if Antiochus would make common cause with Philip against them--the course suggested by the position of affairs, as well as by the treaty of alliance.
But, not far-seeing enough to repel at once with all his energy any interference whatever by the Romans in the affairs of the east, Antiochus thought that his best course was to take advantage of the subjugation of Philip by the Romans (which might easily be foreseen), in order to secure the kingdom of Egypt, which he had previously been willing to share with Philip, for himself alone.
Notwithstanding the close relations of Rome with the court of Alexandria and her royal ward, the senate by no means intended to be in reality, what it was in name, his "protector;" firmly resolved to give itself no concern about Asiatic affairs except in case of extreme necessity, and to limit the sphere of the Roman power by the Pillars of Hercules and the Hellespont, it allowed the great-king to take his course. He himself was not probably in earnest with the conquest of Egypt proper--which was more easily talked of than achieved--but he contemplated the subjugation of the foreign possessions of Egypt one after another, and at once attacked those in Cilicia as well as in Syria and Palestine.
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Reference address : https://www.ellopos.net/elpenor/rome/3-09-war-antiochus-asia.asp?pg=2