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
It was painful doubtless, but yet of itself conducive to the rightly understood interest of the aristocracy, if, as could not but be the effect of the Sulpician proposal, all individuals should withdraw from the senate who were unable speedily to meet their liabilities, and if the coterie-system, which found its main support in the insolvency of many senators and their consequent dependence on their wealthy colleagues, should be checked by the removal of the notoriously venal pack of the senators.
At the same time, of course, we do not mean to deny that such a purification of the senate-house so abruptly and invidiously exposing the senate, as Rufus proposed, would certainly never have been proposed without his personal quarrels with the ruling coterie-heads. Lastly, the regulationin favour of the freedmen had undoubtedly for its primary object to make its proposer master of the street; but in itself it was neither unwarranted nor incompatible with the aristocratic constitution.
Since the freedmen had begun to be drawn upon for military service, their demand for the right of voting was so far justified, as the right of voting and the obligation of service had always gone hand in hand. Moreover, looking to the nullity of the comitia, it was politically of very little moment whether one sewer more emptied itself into that slough.
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Reference address : https://www.ellopos.net/elpenor/rome/4-07-sulpician-revolution.asp?pg=62