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
Gracchus renewed the rule--which presumably was often violently infringed--that no burgess should be enlisted in the army before the commencement of his eighteenth year; and also, apparently, restricted the number of campaigns requisite for full exemption from military duty. Besides, the clothing of the soldiers, the value of which had hitherto been deducted from their pay, was henceforward furnished gratuitously by the state.
To this head belongs, moreover, the tendency which is on various occasions apparent in the Gracchan legislation, if not to abolish capital punishment, at any rate to restrict it still further than had been done before--a tendency, which to some extent made itself felt even in military jurisdiction. From the very introduction of the republic the magistrate had lost the right of inflicting capital punishment on the burgess without consulting the community, except under martial law;(15) if this right of appeal by the burgess appears soon after the period of the Gracchi available even in the camp, and the right of the general to inflict capital punishments appears restricted to allies and subjects, the source of the change is probably to be sought in the law of Gaius Gracchus -de provocatione- But the right of the community to inflict or rather to confirm sentence of death was indirectly yet essentially limited by the fact, that Gracchus withdrew the cognizance of those public crimes which most frequently gave occasion to capital sentences--poisoning and murder generally-- from the burgesses, and entrusted it to permanent judicial commissions.
15. Cf. II. I. Right of Appeal; II. VIII. Changes in Procedure
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Reference address : https://www.ellopos.net/elpenor/rome/4-03-revolution-gaius-gracchus.asp?pg=22