The traditionally early extant bodies of law, such as the Twelve Tables from the early republic, were of little chronological value, and juristic commentarii were liable to mislead through their zeal for precedent, while Cicero, in spite of Polybius’ claim to have inspected early treaties preserved in the Capitol definitely states that there were no public records of early laws. A source frequently referred to is the Annales maximi, a collection made about 130 bc of the annual notices displayed on a white board by the pontifices and containing notes of food prices, eclipses, etc. Dionysius of Halicarnassus implied that they gave a date for the foundation of the city but was reluctant to accept their authority; and one of the eclipses is referred to by Cicero as being mentioned also by Ennius, but unfortunately the number of the year “from the foundation of the city” is corrupt in the text. Although it is possible to calculate the dates of eclipses astronomically in terms of the modern era, it is difficult to link these to Roman chronology because of the uncertainty of the figures and because of the confused state of the Roman calendar before the Julian reform (see calendar: The early Roman calendar). Another difficulty is that the early records may have been burned in 390 bc when Celtic tribes sacked the city; also they would probably have been largely unintelligible if authentic.

Livy quoted the 1st-century annalist Gaius Licinius Macer as having found in the temple of Juno Moneta “linen rolls” giving lists of magistrates; but he also said that Macer and Quintus Aelius Tubero both cited the rolls for the consuls of 434 but gave different names. In any case, it is unlikely that the list could have been older than the temple, which dates from 344 bc. It is clear that the chief sources for the lists were the pedigrees of prominent Roman families, such as the Claudii Marcelli, Fabii, and Aemilii, drawn up by Atticus; but Cicero and Livy agree that tendentious falsifications had in many cases corrupted the records, and other suspicious facts are the appearance of obviously later or invented cognomina, or third names, and of plebeian gentile names for the earliest period, when only patricians bore them. Many scholars, however, accept the general authenticity of the lists—one reason being the appearance in them of extinct patrician families—but prefer Livy’s version to that of the Capitoline lists, which show signs of late revision, often give names in incorrect order, and contain other anomalies.

The question, therefore, remains whether Roman chronography was dependent on the lists of magistrates or whether these were adapted to fit other known datings. The apparent advantages of the existence of a terminal date, the “foundation of the city,” is illusory for Roman chronology, since it depended on back reckoning and was not agreed even in antiquity. Various ancient scholars each assumed a different date. Each computed his date by adding a different number of years of kingly rule from the foundation of the city to his estimate of the date of the foundation of the republic. This, in turn, was presumably computed by counting back over the yearly lists of magistrates. There may have been traditions about the intervals between certain events in early Roman history, but the frequently accepted reckoning of 244 years of kingly rule seems to be a calculation based only on the conventional 35-year generation for the rule of the seven legendary kings. Polybius claimed that the dating of the first republican consulship to 508/507 bc could be substantiated by an extant copy of a contemporary treaty. Combined with the traditional kingly period, this would give a foundation date of 751–750, reckoned inclusively, and 752–751, exclusively (Cato’s date). The chronological scheme worked out by Varro added two years of nonconsular rule, thus the foundation of Rome was put in 754/753 and the beginning of the republic in 510/509. Varro’s dates became standard for later Romans and are sometimes also used by modern scholars in a purely conventional sense. But it remains uncertain whether the dating depended on the magistrate lists or whether these were “doctored” to synchronize with given dates or intervals, whether these were traditional or calculated in some other way. Anomalies such as Livy’s five-year anarchy 15 years after the Gallic invasion, Diodorus’ repetition of magistrates’ names, and the “dictator years” in the lists are perhaps attempts to synchronize the various pedigrees.

Contribution of archaeology

Archaeology can provide many dates useful to the detailed study of Roman history, especially from coins and inscriptions, but, for the general scheme of early chronology, its value is largely negative. It shows, for example, that Rome evolved over a lengthy period and was not really “founded,” though a “foundation” date might perhaps refer to the first common celebration of the Septimontium, or festival of the seven hills; again, if that dating is dependent on the seven kings, archaeology shows that the tradition about them, though it may preserve genuine names and events, is largely legendary.

Datings after the 1st century bc

In this better documented period, datings to consul years, or later to the years of tribunician power of the emperors, are normally intelligible, despite a few notorious cruxes, although up to the Julian reform the state of the calendar has always to be taken into account. In parts of the empire, however, different eras were used—e.g., that of the Seleucids—and from the 4th century ad dates were often calculated in terms of the years of the indiction, a 15-year cycle connected with the levying of taxes, a method that continued in use for many centuries in spite of difficulties, such as lack of synchronization among the various provinces.