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
Government of the Patriciate
Time however was required for the development of these consequences of the new republicanism; vividly as posterity felt its effects, the revolution probably appeared to the contemporary world at first in a different light. The non-burgesses indeed gained by it burgess-rights, and the new burgess-body acquired in the -comitia centuriata- comprehensive prerogatives; but the right of rejection on the part of the patrician senate, which in firm and serried ranks confronted the -comitia- as if it were an Upper House, legally hampered their freedom of movement precisely in the most important matters, and although not in a position to thwart the serious will of the collective body, could yet practically delay and cripple it.
If the nobility in giving up their claim to be the sole embodiment of the community did not seem to have lost much, they had in other respects decidedly gained. The king, it is true, was a patrician as well as the consul, and the right of nominating the members of the senate belonged to the latter as to the former; but while his exceptional position raised the former no less above the patricians than above the plebeians, and while cases might easily occur in which he would be obliged to lean upon the support of the multitude even against the nobility, the consul--ruling for a brief term, but before and after that term simply one of the nobility, and obeying to-morrow the noble fellow-burgess whom he had commanded to-day--by no means occupied a position aloof from his order, and the spirit of the noble in him must have been far more powerful than that of the magistrate.
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Reference address : https://www.ellopos.net/elpenor/rome/2-01-constitution-magistrate.asp?pg=33