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
The distribution was
accordingly designed to go on for an indefinite period until the
Italian domains which were very extensive and difficult of adjustment
should be regulated. The new features in the Sempronian agrarian law,
as compared with the Licinio-Sextian, were, first, the clause in favour
of the hereditary possessors; secondly, the leasehold and inalienable
tenure proposed for the new allotments; thirdly and especially, the
regulated and permanent executive, the want of which under the older
law had been the chief reason why it had remained without lasting
practical application.
War was thus declared against the great landholders, who now, as
three centuries ago, found substantially their organ in the senate;
and once more, after a long interval, a single magistrate stood forth
in earnest opposition to the aristocratic government. It took up the
conflict in the mode--sanctioned by use and wont for such cases--of
paralyzing the excesses of the magistrates by means of the magistracy
itself.(31)