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
Preparations and Pretexts for Second Macedonian War
Thus in reality all political, commercial, and moral motives concurred in inducing Rome to undertake the second war against Philip--one of the most righteous, which the city ever waged. It greatly redounds to the honour of the senate, that it immediately resolved on its course and did not allow itself to be deterred from making the necessary preparations either by the exhaustion of the state or by the unpopularity of such a declaration of war. The propraetor Marcus Valerius Laevinus made his appearance as early as 553 with the Sicilian fleet of 38 sail in the eastern waters.
The government, however, were at a loss to discover an ostensible pretext for the war; a pretext which they needed in order to satisfy the people, even although they had not been far too sagacious to undervalue, as was the manner of Philip, the importance of assigning a legitimate ground for hostilities. The support, which Philip was alleged to have granted to the Carthaginians after the peace with Rome, manifestly could not be proved.
The Roman subjects, indeed, in the province of Illyria had for a considerable time complained of the Macedonian encroachments. In 551 a Roman envoy at the head of the Illyrian levy had driven Philip's troops from the Illyrian territory; and the senate had accordingly declared to the king's envoys in 552, that if he sought war, he would find it sooner than was agreeable to him.
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Reference address : https://www.ellopos.net/elpenor/rome/3-08-second-macedonian-war.asp?pg=30