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 six "bird-carriers" (-augures-) were skilled in interpreting the language of the gods from the flight of birds; an art which was prosecuted with great earnestness and reduced to a quasi-scientific system. The six "bridge-builders" (-Pontifices-) derived their name from their function, as sacred as it was politically important, of conducting the building and demolition of the bridge over the Tiber.
They were the Roman engineers, who understood the mystery of measures and numbers; whence there devolved upon them also the duty of managing the calendar of the state, of proclaiming to the people the time of new and full moon and the days of festivals, and of seeing that every religious and every judicial act took place on the right day. As they had thus an especial supervision of all religious observances, it was to them in case of need--on occasion of marriage, testament, and -adrogatio- --that the preliminary question was addressed, whether the business proposed did not in any respect offend against divine law; and it was they who fixed and promulgated the general exoteric precepts of ritual, which were known under the name of the "royal laws."
Thus they acquired (although not probably to the full extent till after the abolition of the monarchy) the general oversight of Roman worship and of whatever was connected with it--and what was there that was not so connected? They themselves described the sum of their knowledge as "the science of things divine and human." In fact the rudiments of spiritual and temporal jurisprudence as well as of historical recording proceeded from this college.
For all writing of history was associated with the calendar and the book of annals; and, as from the organization of the Roman courts of law no tradition could originate in these courts themselves, it was necessary that the knowledge of legal principles and procedure should be traditionally preserved in the college of the Pontifices, which alone was competent to give an opinion respecting court-days and questions of religious law.
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Reference address : https://www.ellopos.net/elpenor/rome/1-12-religion.asp?pg=18