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
The later historians were evidently unable to construct a readable and in some measure connected narrative out of these notices from the book of annals; and we should have difficulty, even if the book of annals still lay before us with its original contents, in writing from it in duly connected sequence the history of the times.
Such chronicles, however, did not exist merely in Rome; every Latin city possessed its annals as well as its pontifices, as is clear from isolated notices relative to Ardea for instance, Ameria, and Interamna on the Nar; and from the collective mass of these city-chronicles some result might perhaps have been attained similar to what has been accomplished for the earlier middle ages by the comparison of different monastic chronicles. Unfortunately the Romans in later times preferred to supply the defect by Greek or Hellenizing falsehoods.
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Reference address : https://www.ellopos.net/elpenor/rome/2-09-art-science.asp?pg=12