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
When Caesar in 690 brought the executioners of Sulla before the commission for murder(20) he allowed the rest to be condemned, but the most guilty and infamous of all, Catilina, to be acquitted.
20. Cf. V. V. Rehabilitation of Saturninus and Marius
In the revelations of the 3rd of December, it is true, Cicero did not include among the names of the conspirators of whom he had information those of the two influential men; but it is notorious that the informers denounced not merely those against whom subsequently investigation was directed, but "many innocent" persons besides, whom the consul Cicero thought proper to erase from the list; and in later years, when he had no reason to disguise the truth, he expressly named Caesar among the accomplices. An indirect but very intelligible inculpation is implied also in the circumstance, that of the four persons arrested on the 3rd of December the two least dangerous, Statilius and Gabinius, were handed over to be guarded by the senators Caesar and Crassus; it was manifestly intended that these should either, if they allowed them to escape, be compromised in the view of public opinion as accessories, or, if they really detained them, be compromised in the view of their fellow-conspirators as renegades.
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Reference address : https://www.ellopos.net/elpenor/rome/5-05-parties-pompeius.asp?pg=43