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
Another disadvantage arises from the frequency with which the river overflows its banks. Its very slight fall renders it unable to carry off the water, which during the rainy season descends in large quantities from the mountains, with sufficient rapidity to the sea, and in consequence it floods the low-lying lands and the valleys that open between the hills, and converts them into swamps. For a settler the locality was anything but attractive. In antiquity itself an opinion was expressed that the first body of immigrant cultivators could scarce have spontaneously resorted in search of a suitable settlement to that unhealthy and unfruitful spot in a region otherwise so highly favoured, and that it must have been necessity, or rather some special motive, which led to the establishment of a city there.
Even the legend betrays its sense of the strangeness of the fact: the story of the foundation of Rome by refugees from Alba under the leadership of the sons of an Alban prince, Romulus and Remus, is nothing but a naive attempt of primitive quasi-history to explain the singular circumstance of the place having arisen on a site so unfavourable, and to connect at the same time the origin of Rome with the general metropolis of Latium. Such tales, which profess to be historical but are merely improvised explanations of no very ingenious character, it is the first duty of history to dismiss; but it may perhaps be allowed to go a step further, and after weighing the special relations of the locality to propose a positive conjecture not regarding the way in which the place originated, but regarding the circumstances which occasioned its rapid and surprising prosperity and led to its occupying its peculiar position in Latium.
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Reference address : https://www.ellopos.net/elpenor/rome/1-04-beginnings-rome.asp?pg=5