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
Now at length, when civil war was imminent and the conflict in the streets might hourly begin, the decemvirs renounced their usurped and dishonoured power; and the consuls Lucius Valerius and Marcus Horatius negotiated a second compromise, by which the tribunate of the plebs was again established. The impeachment of the decemvirs terminated in the two most guilty, Appius Claudius and Spurius Oppius, committing suicide in prison, while the other eight went into exile and the state confiscated their property. The prudent and moderate tribune of the plebs, Marcus Duilius, prevented further judicial prosecutions by a seasonable use of his veto.
So runs the story as recorded by the pen of the Roman aristocrats; but, even leaving out of view the accessory circumstances, the great crisis out of which the Twelve Tables arose cannot possibly have ended in such romantic adventures, and in political issues so incomprehensible. The decemvirate was, after the abolition of the monarchy and the institution of the tribunate of the people, the third great victory of the plebs; and the exasperation of the opposite party against the institution and against its head Appius Claudius is sufficiently intelligible.
The plebeians had through its means secured the right of eligibility to the highest magistracy of the community and a general code of law; and it was not they that had reason to rebel against the new magistracy, and to restore the purely patrician consular government by force of arms. This end can only have been pursued by the party of the nobility, and if the patricio-plebeian decemvirs made the attempt to maintain themselves in office beyond their time, the nobility were certainly the first to enter the lists against them; on which occasion doubtless the nobles would not neglect to urge that the stipulated rights of the plebs should be curtailed and the tribunate, in particular, should be taken from it. If the nobility thereupon succeeded in setting aside the decemvirs, it is certainly conceivable that after their fall the plebs should once more assemble in arms with a view to secure the results both of the earlier revolution of 260 and of the latest movement; and the Valerio-Horatian laws of 305 can only be understood as forming a compromise in this conflict.
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Reference address : https://www.ellopos.net/elpenor/rome/2-02-tribunate-plebs-decemvirate.asp?pg=36