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
Political Effects of the Servian Military Organization
It is evident at a glance that this whole institution was from the outset of a military nature. In the whole detailed scheme we do not encounter a single feature suggestive of any destination of the centuries to other than purely military purposes; and this alone must, with every one accustomed to consider such matters, form a sufficient reason for pronouncing its application to political objects a later innovation. If, as is probable, in the earliest period every one who had passed his sixtieth year was excluded from the centuries, this has no meaning, so far as they were intended from the first to form a representation of the burgess-community similar to and parallel with the curies.
Although, however, the organization of the centuries was introduced merely to enlarge the military resources of the burgesses by the inclusion of the μέτοικοι and, in so far, there is no greater error than to exhibit the Servian organization as the introduction of a timocracy in Rome--yet the new obligation imposed upon the inhabitants to bear arms exercised in its consequences a material influence on their political position. He who is obliged to become a soldier must also, so long as the state is not rotten, have it in his power to become an officer; beyond question plebeians also could now be nominated in Rome as centurions and as military tribunes.
Although, moreover, the institution of the centuries was not intended to curtail the political privileges exclusively possessed by the burgesses as hitherto represented in the curies, yet it was inevitable that those rights, which the burgesses hitherto had exercised not as the assembly of curies, but as the burgess-levy, should pass over to the new centuries of burgesses and μέτοικοι. Henceforward, accordingly, it was the centuries whose consent the king had to ask before beginning an aggressive war.(11)
11. Cf. I. V. Burdens of the Burgesses
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Reference address : https://www.ellopos.net/elpenor/rome/1-06-burgesses-reformed-constitution.asp?pg=19