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
Lastly it was added that the holding of the tribunate should in future disqualify for the undertaking of a higher office--an enactment which, like many other points in Sulla's restoration, once more reverted to the old patrician maxims, and, just as in the times before the admission of the plebeians to the civil magistracies, declared the tribunate and the curule offices to be mutually incompatible.
In this way the legislator of the oligarchy hoped to check tribunician demagogism and to keep all ambitious and aspiring men aloof from the tribunate, but to retain it as an instrument of the senate both for mediating between it and the burgesses, and, should circumstances require, for keeping in check the magistrates; and, as the authority of the king and afterwards of the republican magistrates over the burgesses scarcely anywhere comes to light so clearly as in the principle that they exclusively had the right of addressing the people, so the supremacy of the senate, now first legally established, is most distinctly apparent in this permission which the leader of the people had to ask from the senate for every transaction with his constituents.
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Reference address : https://www.ellopos.net/elpenor/rome/4-10-sullan-constitution.asp?pg=31