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
Apart from the fact that they took up for service in the fleet the persons of free birth rated between 4000 -asses- (17 pounds) and 1500 -asses- (6 pounds) and all the freedmen, the minimum census for the legionary was reduced to 4000 -asses- (17 pounds); and, in case of need, both those who were bound to serve in the fleet and the free-born rated between 1500 -asses- (6 pounds) and 375 -asses- (1 pound 10 shillings) were enrolled in the burgess-infantry.
These innovations, which belong presumably to the end of the preceding or beginning of the present epoch, doubtless did not originate in party efforts any more than did the Servian military reform; but they gave a material impulse to the democratic party, in so far as those who bore civic burdens necessarily claimed and eventually obtained equalization of civic rights.
The poor and the freedmen began to be of some importance in the commonwealth from the time when they served it; and chiefly from this cause arose one of the most important constitutional changes of this epoch --the remodelling of the -comitia centuriata-, which most probably took place in the same year in which the war concerning Sicily terminated
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Reference address : https://www.ellopos.net/elpenor/rome/3-11-government-governed.asp?pg=69