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 same tendency showed itself in a more important matter, or to speak more correctly in the vital question for Rome--the system of colonization. It needed no special wisdom, but merely a recollection of the course of the first social crisis in Rome, to perceive that the only real remedy against an agricultural proletariate consisted in a comprehensive and duly-regulated system of emigration;(19) for which the external relations of Rome offered the most favourable opportunity.
19. Cf. II. III. Influence of the Extension of the Roman Dominion in Elevating the Farmer-Class
Until nearly the close of the sixth century, in fact, the continuous diminution of the small landholders of Italy was counteracted by the continuous establishment of new farm-allotments.(20)
20. Cf. III. XI. Assignations of Land
This, it is true, was by no means done to the extent to which it might and should have been done; not only was the domain-land occupied from ancient times by private persons(21) not recalled, but further occupations of newly-won land were permitted; and other very important acquisitions, such as the territory of Capua, while not abandoned to occupation, were yet not brought into distribution, but were let on lease as usufructuary domains.
21. Cf. II. II. Public Land
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Reference address : https://www.ellopos.net/elpenor/rome/4-02-reform-tiberius-gracchus.asp?pg=26