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
Nasica, against whom above all others the multitude breathed vengeance, and who had at least the courage openly to avow his deed before the people and to defend it, was under honourable pretexts despatched to Asia, and soon afterwards (624) invested, during his absence, with the office of Pontifex Maximus. Nor did the moderate party dissociate themselves from these proceedings of their colleagues.
Gaius Laelius bore a part in the investigations adverse to the partisans of Gracchus; Publius Scaevola, who had attempted to prevent the murder, afterwards defended it in the senate; when Scipio Aemilianus, after his return from Spain (622), was challenged publicly to declare whether he did or did not approve the killing of his brother-in-law, he gave the at least ambiguous reply that, so far as Tiberius had aspired to the crown, he had been justly put to death.
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Reference address : https://www.ellopos.net/elpenor/rome/4-02-reform-tiberius-gracchus.asp?pg=49