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
This new organization of the army was accompanied by a more careful supervision of landed property on the part of the state. It was now either ordained for the first time or, if not, at any rate defined more carefully, that a land-register should be established, in which the several proprietors of land should have their fields with all their appurtenances, servitudes, slaves, beasts of draught and of burden, duly recorded.
Every act of alienation, which did not take place publicly and before witnesses, was declared null; and a revision of the register of landed property, which was at the same time the levy-roll, was directed to be made every fourth year. The -mancipatio- and the -census- thus arose out of the Servian military organization.
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Reference address : https://www.ellopos.net/elpenor/rome/1-06-burgesses-reformed-constitution.asp?pg=18