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 further attempt was made to get rid of the tribunician power by securing to the plebeians equality of rights in a more regular and more effectual way. The tribune of the people, Gaius Terentilius Arsa, proposed in 292 the nomination of a commission of five men to prepare a general code of law by which the consuls should in future be bound in exercising their judicial powers. But the senate refused to sanction this proposal, and ten years elapsed ere it was carried into effect--years of vehement strife between the orders, and variously agitated moreover by wars and internal troubles.
With equal obstinacy the party of the nobles hindered the concession of the law in the senate, and the plebs nominated again and again the same men as tribunes. Attempts were made to obviate the attack by other concessions. In the year 297 an increase of the tribunes from four to ten was sanctioned--a very dubious gain; and in the following year, by an Icilian -plebiscitum- which was admitted among the sworn privileges of the plebs, the Aventine, which had hitherto been a temple-grove and uninhabited, was distributed among the poorer burgesses as sites for buildings in heritable occupancy.
The plebs took what was offered to them, but never ceased to insist in their demand for a legal code. At length, in the year 300, a compromise was effected; the senate in substance gave way. The preparation of a legal code was resolved upon; for that purpose, as an extraordinary measure, the centuries were to choose ten men who were at the same time to act as supreme magistrates in room of the consuls (-decemviri consulari imperio legibus scribundls-), and to this office not merely patricians, but plebeians also might be elected.
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Reference address : https://www.ellopos.net/elpenor/rome/2-02-tribunate-plebs-decemvirate.asp?pg=29