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 intend here to relate the history of Italy, not simply the history of the city of Rome. Although, in the formal sense of political law, it was the civic community of Rome which gained the sovereignty first of Italy and then of the world, such a view cannot be held to express the higher and real meaning of history. What has been called the subjugation of Italy by the Romans appears rather, when viewed in its true light, as the consolidation into an united state of the whole Italian stock--a stock of which the Romans were doubtless the most powerful branch, but still were only a branch.
The history of Italy falls into two main sections: (1) its internal history down to its union under the leadership of the Latin stock, and (2) the history of its sovereignty over the world. Under the first section, which will occupy the first two books, we shall have to set forth the settlement of the Italian stock in the peninsula; the imperilling of its national and political existence, and its partial subjugation, by nations of other descent and older civilization, Greeks and Etruscans; the revolt of the Italians against the strangers, and the annihilation or subjection of the latter; finally, the struggles between the two chief Italian stocks, the Latins and the Samnites, for the hegemony of the peninsula, and the victory of the Latins at the end of the fourth century before the birth of Christ--or of the fifth century of the city. The second section opens with the Punic wars; it embraces the rapid extension of the dominion of Rome up to and beyond the natural boundaries of Italy, the long status quo of the imperial period, and the collapse of the mighty empire. These events will be narrated in the third and following books.
Note: The dates as hereafter inserted in the text are years of the City (A.U.C.); those in the margin give the corresponding years B.C.
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : https://www.ellopos.net/elpenor/rome/1-01-abolition-monarchy.asp?pg=4