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
When and how the distribution of the arable land took place, can no longer be ascertained. This much only is certain, that the oldest form of the constitution was based not on freehold settlement, but on clanship as a substitute for it, whereas the Servian constitution presupposes the distribution of the land.
It is evident from the same constitution that the great bulk of the landed property consisted of middle-sized farms, which provided work and subsistence for a family and admitted of the keeping of cattle for tillage as well as of the application of the plough. The ordinary extent of such a Roman full hide has not been ascertained with precision, but can scarcely, as has already been shown,(7) be estimated at less than twenty -jugera-(12 1/2 acres nearly).
7. Cf. I. VI. Time and Occasion of the Reform
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Reference address : https://www.ellopos.net/elpenor/rome/1-13-agriculture-trade-commerce.asp?pg=5