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
Marius Nominated Commander-in-Chief in Sulla's Stead
But, be this as it might, Sulpicius, with a view to parry the presumed blow, conceived the scheme of taking the supreme command from Sulla; and for this purpose joined with Marius, whose name was still sufficiently popular to make a proposal to transfer to him the chief command in the Asiatic war appear plausible to the multitude, and whose military position and ability might prove a support in the event of a rupture with Sulla.
Sulpicius probably did not overlook the danger involved in placing that old man--not less incapable than vengeful and ambitious--at the head of the Campanian army, and as little the scandalous irregularity of entrusting an extraordinary supreme command by decree of the people to a private man; but the very tried incapacity of Marius as a statesman gave a sort of guarantee that he would not be able seriously to endanger the constitution, and above all the personal position of Sulpicius, if he formed a correct estimate of Sulla's designs, was one of so imminent peril that such considerations could hardly be longer heeded.
That the worn-out hero himself readily met the wishes of any one who would employ him as a -condottiere-, was a matter of course; his heart had now for many years longed for the command in an Asiatic war, and not less perhaps for an opportunity of once settling accounts thoroughly with the majority of the senate. Accordingly on the proposal of Sulpicius Gaius Marius was by decree of the people invested with extraordinary supreme, or as it was called proconsular, power, and obtained the command of the Campanian army and the superintendence of the war against Mithradates; and two tribunes of the people were despatched to the camp at Nola, to take over the army from Sulla.
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Reference address : https://www.ellopos.net/elpenor/rome/4-07-sulpician-revolution.asp?pg=66