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
Revolt of the Slaves
But nowhere did the impotence and perversity of the Roman provincial administration come to light so conspicuously as in the insurrections of the slave proletariate, which seemed to have revived on their former footing simultaneously with the restoration of the aristocracy.
These insurrections of the slaves swelling from revolts into wars-- which had emerged just about 620 as one, and that perhaps the proximate, cause of the Gracchan revolution--were renewed and repeated with dreary uniformity. Again, as thirty years before, a ferment pervaded the body of slaves throughout the Roman empire. We have already mentioned the Italian conspiracies.
The miners in the Attic silver-mines rose in revolt, occupied the promontory of Sunium, and issuing thence pillaged for a length of time the surrounding country. Similar movements appeared at other places.
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Reference address : https://www.ellopos.net/elpenor/rome/4-04-rule-restoration.asp?pg=18