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
In a military point of view, no doubt, we find some honourable exceptions of able officers belonging to the highest circles of the aristocracy; but the rule was, that the lords of quality, when they were to assume the command of armies, hastily read up from the Greek military manuals and the Roman annals as much as was required for holding a military conversation, and then, when in the field, acted most wisely by entrusting the real command to an officer of humble lineage but of tried capacity and tried discretion. In fact, if a couple of centuries earlier the senate resembled an assembly of kings, these their successors played not ill the part of princes.
But the incapacity of these restored aristocrats was fully equalled by their political and moral worthlessness. If the state of religion, to which we shall revert, did not present a faithful reflection of the wild dissoluteness of this epoch, and if the external history of the period did not exhibit the utter depravity of the Roman nobles as one of its most essential elements, the horrible crimes, which came to light in rapid succession among the highest circles of Rome, would alone suffice to indicate their character.
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Reference address : https://www.ellopos.net/elpenor/rome/4-04-rule-restoration.asp?pg=15