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
By the side of these two oldest and most eminent corporations of men versed in spiritual lore may be to some extent ranked the college of the twenty state-heralds (-fetiales-, of uncertain derivation), destined as a living repository to preserve traditionally the remembrance of the treaties concluded with neighbouring communities, to pronounce an authoritative opinion on alleged infractions of treaty-rights, and in case of need to attempt reconciliation or declare war. They had precisely the same position with reference to international, as the Pontifices had with reference to religious, law; and were therefore, like the latter, entitled to point out the law, although not to administer it.
But in however high repute these colleges were, and important and comprehensive as were the functions assigned to them, it was never forgotten--least of all in the case of those which held the highest position--that their duty was not to command, but to tender skilled advice, not directly to obtain the answer of the gods, but to explain the answer when obtained to the inquirer. Thus the highest of the priests was not merely inferior in rank to the king, but might not even give advice to him unasked.
It was the province of the king to determine whether and when he would take an observation of birds; the "bird-seer" simply stood beside him and interpreted to him, when necessary, the language of the messengers of heaven. In like manner the Fetialis and the Pontifex could not interfere in matters of international or common law except when those concerned therewith desired it. The Romans, notwithstanding all their zeal for religion, adhered with unbending strictness to the principle that the priest ought to remain completely powerless in the state and--excluded from all command-- ought like any other burgess to render obedience to the humblest magistrate.
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Reference address : https://www.ellopos.net/elpenor/rome/1-12-religion.asp?pg=19