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
While in jurisdiction they stood from the beginning on an equality with the consuls and in the early stages of the conflicts between the orders acquired like the consuls the right of initiating legislation, they now received--we know not exactly when, but presumably at or soon after the final equalization of the orders--a position of equality with the consuls as confronting the practically governing authority, the senate.
Hitherto they had been present at the proceedings of the senate, sitting on a bench at the door; now they obtained, like the other magistrates and by their side, a place in the senate itself and the right to interpose their word in its discussions. If they were precluded from the right of voting, this was simply an application of the general principle of Roman state-law, that those only should give counsel who were not called to act; in accordance with which the whole of the acting magistrates possessed during their year of office only a seat, not a vote, in the council of the state.(17)
17. Cf. II. I. Senate
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Reference address : https://www.ellopos.net/elpenor/rome/2-03-equalization-orders-aristocracy.asp?pg=51