Oppert's system represents the earliest dates that have been suggested. He accepted the figures of the Kings' List and claimed that he reconciled them with the figures of Berossus, though he ignored the later chronological notices. But there is no evidence for his "cyclic date" of 2517 B.C., on which his system depended, and there is little doubt that the beginning of the historical period of Berossus is to be set, not in 2506 B.C., but in 2232 B.C. The two systems of Sayce, that of Rogers, the three systems of Winckler, both those of Delitzsch, and that of Maspero, may be grouped together, for they are based on the same principle. Having first fixed the date of the close of Dynasty III., they employed the figures of the Kings' List unemended for defining the earlier periods, and did not attempt to reconcile their results with other conflicting data. The difference of eighteen years in Sayce's two dates for the rise of Dynasty I. was due to his employing in 1902 the figures assigned to the first seven kings of the dynasty upon the larger of the two contemporary date-lists, which had meanwhile been published, in place of those given by the List of Kings. It should be noted that Winckler (1905) and Delitzsch (1907) gives the dates only in round numbers.
A second group of systems may be said to consist of those proposed by Lehmann-Haupt, Marquart, Peiser, and Rost, for these writers attempted to get over the discrepancies in the data by emending some of the figures furnished by the inscriptions. In 1891, with the object of getting the total duration of the dynasties to agree with the chronological system of Berossus and with the statement of Nabonidus concerning Khammurabi's date, Peiser proposed to emend the figure given by the Kings' List for the length of Dynasty III. The reading of "9 soss and 36 years," which gives the total 576 years, he suggested was a scribal error for "6 soss and 39 years"; he thus reduced the length of Dynasty III. by 177 years and effected a corresponding reduction in the dates assigned to Dynasties I. and II. In 1897 Rost followed up Peiser's suggestion by reducing the figure still further, but he counteracted to some extent the effects of this additional reduction by emending Sennacherib's date for Marduk-nadin-akhē's defeat of Tiglath-pileser I. as engraved on the rock at Bavian, holding that the figure "418," as engraved upon the rock, was a mistake for "478." Lehmann-Haupt's first system (1898) resembled those of Oppert, Sayce, Rogers, Winckler, Delitzsch and Maspero in that he accepted the figures of the Kings' List, and did not attempt to emend them.
But he obtained his low date for the close of Dynasty III. by emending Sennacherib's figure in the Bavian inscription; this he reduced by a hundred years, instead of increasing it by sixty as Rost had suggested. Lehmann-Haupt's influence is visible in Marquart's system, published in the following year; it may be noted that his slightly reduced figure for the beginning of Dynasty I. was arrived at by incorporating the new information supplied by the first date-list to be published. When revising his scheme of chronology in 1900, Rost abandoned his suggested emendation of Sennacherib's figure, but by decreasing his reduction of the length of Dynasty III., he only altered his date for the beginning of Dynasty I. by one year. In his revised scheme of chronology, published in 1903, Lehmann-Haupt retained his emendation of Sennacherib's figure, and was in his turn influenced by Marquart's method of reconciling the dynasties of Berossus with the Kings' List. He continued to accept the figure of the Kings' List for Dynasty III., but he reduced the length of Dynasty II. by fifty years, arguing that the figures assigned to some of the reigns were improbably high.
His slight reduction in the length of Dynasty I. was obtained from the recently published date-lists, though his proposed reduction of Ammizaduga's reign to ten years has since been disproved.
A third group of systems comprises those proposed by Hommel and Niebuhr, for their reductions in the date assigned to Dynasty I. were effected chiefly by their treatment of Dynasty II. In his first system, published in 1886, Hommel, mainly with the object of reducing Khammurabi's date, reversed the order of the first two dynasties of the Kings' List, placing Dynasty II. before Dynasty I. In his second and third systems (1895 and 1898), and in his second alternative scheme of 1901 (see below), he abandoned this proposal and adopted a suggestion of Halévy that Dynasty III. followed immediately after Dynasty I.; Dynasty II., he suggested, had either synchronized with Dynasty I., or was mainly apocryphal (eine spätere Geschichtskonstruction). Niebuhr's system was a modification of Hommel's second theory, for, instead of entirely ignoring Dynasty II., he reduced its independent existence to 143 years, making it overlap Dynasty I. by 225 years. The extremely low dates proposed by Hommel in 1898 were due to his adoption of Peiser's emendation for the length of Dynasty III., in addition to his own elimination of Dynasty II. In 1901 Hommel abandoned Peiser's emendation and suggested two alternative schemes. According to one of these he attempted to reconcile Berossus with the Kings' List by assigning to Dynasty II. an independent existence of some 171 years, while as a possible alternative he put forward what was practically his theory of 1895.
Such are the principles underlying the various chronological schemes which had, until recently, been propounded. The balance of opinion was in favour of those of the first group of writers, who avoided emendations of the figures and were content to follow the Kings' List and to ignore its apparent discrepancies with other chronological data; but it is now admitted that the general principle underlying the third group of theories was actually nearer the truth. The publication of fresh chronological material in 1906 and 1907 placed a new complexion on the problems at issue, and enabled us to correct several preconceptions, and to reconcile or explain the apparently conflicting data.