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
But the senate not only recalled the general immediately, but after long deliberation caused a proposal to be submitted to the burgesses that the convention should be treated as they had formerly treated that of Caudium, in other words, that they should refuse to ratify it and should devolve the responsibility for it on those by whom it had been concluded. By right this category ought to have included all the officers who had sworn to the treaty; but Gracchus and the others were saved by their connections. Mancinus alone, who did not belong to the circles of the highest aristocracy, was destined to pay the penalty for his own and others' guilt.
Stripped of his insignia, the Roman consular was conducted to the enemy's outposts, and, when the Numantines refused to receive him that they might not on their part acknowledge the treaty as null, the late commander-in-chief stood in his shirt and with his hands tied behind his back for a whole day before the gates of Numantia, a pitiful spectacle to friend and foe. Yet the bitter lesson seemed utterly lost on the successor of Mancinus, his colleague in the consulship, Marcus Aemilius Lepidus.
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Reference address : https://www.ellopos.net/elpenor/rome/4-01-gracchi.asp?pg=22