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
Opinions-- Table of Formulae for Actions
While the mass of written legal documents thus increased, the foundations of jurisprudence in the proper sense were also firmly laid. It was necessary that both the magistrates who were annually changed and the jurymen taken from the people should be enabled to resort to men of skill, who were acquainted with the course of law and knew how to suggest a decision accordant with precedents or, in the absence of these, resting on reasonable grounds.
The pontifices who were wont to be consulted by the people regarding court-days and on all questions of difficulty and of legal observance relating to the worship of the gods, delivered also, when asked, counsels and opinions on other points of law, and thus developed in the bosom of their college that tradition which formed the basis of Roman private law, more especially the formulae of action proper for each particular case.
A table of formulae which embraced all these actions, along with a calendar which specified the court-days, was published to the people about 450 by Appius Claudius or by his clerk, Gnaeus Flavius. This attempt, however, to give formal shape to a science, that as yet hardly recognized itself, stood for a long time completely isolated.
That the knowledge of law and the setting it forth were even now a means of recommendation to the people and of attaining offices of state, may be readily conceived, although the story, that the first plebeian pontifex Publius Sempronius Sophus (consul 450), and the first plebeian pontifex maximus Tiberius Coruncanius (consul 474), were indebted for these priestly honours to their knowledge of law, is probably rather a conjecture of posterity than a statement of tradition.
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Reference address : https://www.ellopos.net/elpenor/rome/2-09-art-science.asp?pg=26