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
In Italy it was Marcus Tullius Cicero (648-711) who, after having
in his early youth gone along with the Hortensian manner,
was brought by hearing the Rhodian masters and by his own
more matured taste to better paths, and thenceforth addicted himself
to strict purity of language and the thorough periodic arrangement
and modulation of his discourse. The models of language, which,
in this respect he followed, he found especially in those circles
of the higher Roman society which had suffered but little or not at all
from vulgarism; and, as was already said, there were still such,
although they were beginning to disappear.
The earlier Latin
and the good Greek literature, however considerable was the influence
of the latter more especially on the rhythm of his oratory,
were in this matter only of secondary moment: this purifying
of the language was by no means a reaction of the language of books
against that of conversation, but a reaction of the language
of the really cultivated against the jargon of spurious
and partial culture.