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 New Urban Law or the Edict
Commercial intercourse provided for itself a more thorough remedy. The lively intercourse between Romans and non-Romans had long ago developed in Rome an international private law (-ius gentium-;(106)), that is to say, a body of maxims especially relating to commercial matters, according to which Roman judges pronounced judgment, when a cause could not be decided either according to their own or any other national code and they were compelled--setting aside the peculiarities of Roman, Greek, Phoenician and other law-- to revert to the common views of right underlying all dealings.
106. Cf. I. XI. Clients and Foreigners
The formation of the newer law attached itself to this basis. In the first place as a standard for the legal dealings of Roman burgesses with each other, it de facto substituted for the old urban law, which had become practically useless, a new code based in substance on a compromise between the national law of the Twelve Tables and the international law or so-called law of nations. The former was essentially adhered to, though of course with modifications suited to the times, in the law of marriage, family, and inheritance; whereas in all regulations which concerned dealings with property, and consequently in reference to ownership and contracts, the international law was the standard; in these matters indeed various important arrangements were borrowed even from local provincial law, such as the legislation as to usury,(107) and the institution of -hypotheca-.
107. Cf. V. XI. Usury Laws
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Reference address : https://www.ellopos.net/elpenor/rome/5-11-old-republic-new-monarchy.asp?pg=170