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
The Cornelian Freedmen in Rome
Akin to this practical constituting of a standing army for the senate was the measure by which the regent selected from the slaves of the proscribed upwards of 10,000 of the youngest and most vigorous men, and manumitted them in a body. These new Cornelians, whose civil existence was linked to the legal validity of the institutions of their patron, were designed to be a sort of bodyguard for the oligarchy and to help it to command the city populace, on which, indeed, in the absence of a garrison everything in the capital now primarily depended.
Abolition of the Gracchan Institutions
These extraordinary supports on which the regent made the oligarchy primarily to rest, weak and ephemeral as they doubtless might appear even to their author, were yet its only possible buttresses, unless expedients were to be resorted to--such as the formal institution of a standing army in Rome and other similar measures--which would have put an end to the oligarchy far sooner than the attacks of demagogues. The permanent foundation of the ordinary governing power of the oligarchy of course could not but be the senate, with a power so increased and so concentrated that it presented a superiority to its non-organized opponents at every single point of attack.
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Reference address : https://www.ellopos.net/elpenor/rome/4-10-sullan-constitution.asp?pg=18