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
A second consequence of the new union of the burgesses must have been a more definite regulation of the right of settlement, with reference both to the Latin confederates and to other states. It became necessary--not so much on account of the right of suffrage in the centuries (which indeed belonged only to the freeholder) as on account of the right of appeal, which was intended to be conceded to the plebeian, but not to the foreigner dwelling for a time or even permanently in Rome--to express more precisely the conditions of the acquisition of plebeian rights, and to mark off the enlarged burgess-body in its turn from those who were now the non-burgesses.
To thisepoch therefore we may trace back--in the views and feelings of the people--both the invidiousness of the distinction between patricians and plebeians, and the strict and haughty line of demarcation between -cives Romani- and aliens. But the former civic distinction was in its nature transient, while the latter political one was permanent; and the sense of political unity and rising greatness, which was thus implanted in the heart of the nation, was expansive enough first to undermine and then to carry away with its mighty current those paltry distinctions.
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Reference address : https://www.ellopos.net/elpenor/rome/2-01-constitution-magistrate.asp?pg=30