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
Meanwhile Gaius Gracchus reappeared in Rome.
The aristocracy had first sought to detain the object of their dread
in Sardinia by omitting to provide the usual relief, and then, when
without caring for that point he returned, had brought him to trial
as one of the authors of the Fregellan revolt (629-30).
But the
burgesses acquitted him; and now he too threw down the gauntlet,
became a candidate for the tribuneship of the people, and was
nominated to that office for the year 631 in an elective assembly
attended by unusual numbers. War was thus declared.
The democratic
party, always poor in leaders of ability, had from sheer necessity
remained virtually at rest for nine years; now the truce was at an
end, and this time it was headed by a man who, with more honesty
than Carbo and with more talent than Flaccus, was in every respect
called to take the lead.