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 Senate and the Resolutions of the Community: "Patrum Auctoritas"
But it was not merely in so far as the idea of a perpetual kingdom found its living expression in this assembly, that it was an essential member of the Roman constitution. The council of elders, indeed, had no title to interfere with the official functions of the king. The latter doubtless, in the event of his being unable personally to lead the army or to decide a legal dispute, took his deputies at all times from the senate; for which reason subsequently the highest posts of command were regularly bestowed on senators alone, and senators were likewise employed by preference as jurymen.
But the senate, in its collective capacity, was never consulted in the leading of the army or in the administration of justice; and therefore there was no right of military command and no jurisdiction vested in the senate of the later Rome. On the other hand the council of elders was held as called to the guardianship of the existing constitution against encroachments by the king and the burgesses. On the senate devolved the duty of examining every resolution adopted by the burgesses at the suggestion of the king, and of refusing to confirm it if it seemed to violate existing rights; or, which was the same thing, in all cases where a resolution of the community was constitutionally requisite--as on every alteration of the constitution, on the reception of new burgesses, on the declaration of an aggressive war--the council of elders had a right of veto.
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Reference address : https://www.ellopos.net/elpenor/rome/1-05-original-constitution-rome.asp?pg=30