Dionysius of Halicarnassus, Roman Antiquities 5.1.1
1 The Roman monarchy, therefore, after having continued for the space of two hundred and forty-four years from the founding of Rome and having under the last king become a tyranny, was overthrown for the reasons stated and by the men named, at the beginning of the sixty-eighth Olympiad (the one in which Ischomachus of Croton won the foot-race), Isagoras being the annual archon at Athens. 2 An aristocracy being now established, while there still remained about four months to complete that year, Lucius Junius Brutus and Lucius Tarquinius Collatinus were the first consuls invested with the royal power; the Romans, as I have said, call them in their own language consules or "counsellors." These men, associating with themselves many others, now that the soldiers from the camp had come to the city after the truce they had made with the Ardeates, called an assembly of the people a few days after the expulsion of the tyrant, and having spoken at length upon the advantages of harmony, again caused them to pass another vote confirming everything which those in the city had previously voted when condemning the Tarquinii to perpetual banishment. 3 After this they performed rites of purification for the city and entered into a solemn covenant; and they themselves, standing over the parts of the victims, first swore, and then prevailed upon the rest of the citizens likewise to swear, that they would never restore from exile King Tarquinius or his sons or their posterity, and that they would never again make anyone king of Rome or permit others who wished to do so; and this oath they took not only for themselves, but also for their children and their posterity. 4 However, since it appeared that the kings had been the authors of many great advantages to the commonwealth, they desired to preserve the name of that office for as long a time as the city should endure, and accordingly they ordered the pontiffs and augurs to choose from among them the older men the most suitable one for the office, who should have the superintendence of religious observances and of naught else, being exempt from all military and civil duties, and should be called the king of sacred rites. The first person appointed to this office was Manius Papirius, one of the patricians, who was a lover of peace and quiet.
דיוניסיוס ממקם את ראשית הרפובליקה בשנה הראשונה של המשחקים האולימפיים ה-68, השנה שבה איסגוראס (Isagoras) כיהן כארכון באתונה - כלומר שנת 508/7 BC.