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
Law of the Empire
So far as concerns the field of criminal and police law, where the government more directly interferes and the necessities of the case are substantially met by a judicious legislation, there was no difficulty in attaining, in the way of legislative action, that degree of material uniformity which certainly was in this department needful for the unity of the empire. In the civil law again, where the initiative belongs to commercial intercourse and merely the formal shape to the legislator, the code for the united empire, which the legislator certainly could not have created, had been already long since developed in a natural way by commercial intercourse itself.
The Roman urban law was still indeed legally based on the embodiment of the Latin national law contained in the Twelve Tables. Later laws had doubtless introduced various improvements of detail suited to the times, among which the most important was probably the abolition of the old inconvenient mode of commencing a process through standing forms of declaration by the parties(104) and the substitution of an instruction drawn up in writing by the presiding magistrate for the single juryman (formula): but in the main the popular legislation had only piled upon that venerable foundation an endless chaos of special laws long since in great part antiquated and forgotten, which can only be compared to the English statute-law.
104. Cf. I. XI. Character of the Roman Law
The attempts to impart to them scientific shape and system had certainly rendered the tortuous paths of the old civil law accessible, and thrown light upon them;(105) but no Roman Blackstone could remedy the fundamental defect, that an urban code composed four hundred years ago with its equally diffuse and confused supplements was now to serve as the law of a great state.
105. Cf. IV. XIII. Philology
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Reference address : https://www.ellopos.net/elpenor/rome/5-11-old-republic-new-monarchy.asp?pg=169