Nabonassar (747 B.C.) .
With Nabu-nazir, the Nabonassar of classical writers, the socalled Canon of Ptolemy begins.
760 Nabonassar, 14 years.
II.) gives a list of the Babylonian, Assyrian and Persian kings who ruled in Babylon, together with the number of years each of them reigned, from the accession of Nabonassar in 747 B.C. to the conquest of Babylon by Alexander the Great in 331 B.C. The accuracy of this list is confirmed by the larger List of Kings and by the principal Babylonian Chronicle; the latter, like the Canon, begins with the reign of Nabonassar, who, it has been suggested, may have revised the calendar and have inaugurated a new epoch for the later chronology.
This omission is much to be regretted, since Nabonassar was the last king but two of this dynasty, and, had we known its duration, we could have combined the information on the earlier periods furnished by the Kings' List with the evidence of the Ptolemaic Canon.
In the history of Babylonia, the fixed point from which time was reckoned was the era of Nabonassar, 747 B.C. Among the Greeks the reckoning was by Olympiads, the point of departure being the year in which Coroebus was victor in the Olympic Games, 776 B.C. The Roman chronology started from the foundation of the city, the year of which, however, was variously given by different authors.
It is believed to have been in use from the very time of its origin; for the observations of eclipses which were collected in Chaldaea by Callisthenes, the general of Alexander, and transmitted by him to Aristotle, were for the greater part referred to the beginning of the reign of Nabonassar, founder of the kingdom of the Babylonians.
On account of the difference in the length of the Julian and Babylonian years, the conversion of dates according to the era of Nabonassar into years before Christ is attended with considerable trouble.
The Greeks of Alexandria formerly employed the era of Nabonassar, with a year of 365 days; but soon after the reformation of the calendar of Julius Caesar, they adopted, like other Roman provincials, the Julian intercalation.
It may be explained here that the dates of the Assyrian and Babylonian kings can be reduced to years B.C. by means of the socalled " Canon of Ptolemy," which is a list of the Babylonian and Persian kings, with the lengths of their reigns, extending from Nabonassar, 747 B.C., to Alexander the Great, drawn up in the 2nd century A.D.