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
We have already mentioned the great roads and fortresses instituted for permanently securing Apulia and above all Campania: by their means Samnium was further surrounded on the east and west with the net of Roman strongholds. It is a significant token of the comparative weakness of Etruria that it was not deemed necessary to secure the passes through the Ciminian Forest in a similar mode--by a highway and corresponding fortresses. The former frontier fortress of Sutrium continued to be in this quarter the terminus of the Roman military line, and the Romans contented themselves with having the road leading thence to Arretium kept in a serviceable state for military purposes by the communities through whose territories it passed.(4)
4. The operations in the campaign of 537, and still more plainly the formation of the highway from Arretium to Bononia in 567, show that the road from Rome to Arretium had already been rendered serviceable before that time. But it cannot at that period have been a Roman military road, because, judging from its later appellation of the "Cassian way," it cannot have been constructed as a -via consularis- earlier than 583; for no Cassian appears in the lists of Roman consuls and censors between Spurius Cassius, consul in 252, 261, and 268--who of course is out of the question--and Gaius Cassius Longinus, consul in 583.
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : https://www.ellopos.net/elpenor/rome/2-06-italians-rome.asp?pg=30