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 evening had come on, the bodies were thrown into the Tiber; Gaius vainly entreated that the corpse of his brother might be granted to him for burial. Such a day had never before been seen by Rome. The party-strife lasting for more than a century during the first social crisis had led to no such catastrophe as that with which the second began. The better portion of the aristocracy might shudder, but they could no longer recede. They had no choice save to abandon a great number of their most trusty partisans to the vengeance of the multitude, or to assume collectively the responsibility of the outrage: the latter course was adopted.
They gave official sanction to the assertion that Gracchus had wished to seize the crown, and justified this latest crime by the primitive precedent of Ahala;(33) in fact, they even committed the duty of further investigation as to the accomplices of Gracchus to a special commission and made its head, the consul Publius Popillius, take care that a sort of legal stamp should be supplementarily impressed on the murder of Gracchus by bloody sentences directed against a large number of inferior persons (622).
33. Cf. II. III. Attempts at Counter-Revolution
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Reference address : https://www.ellopos.net/elpenor/rome/4-02-reform-tiberius-gracchus.asp?pg=48