3) The Septuagint was not created just for the Library of Alexandria. The Greek text was distributed far and wide. One copy was always at the disposal of the Jewish high priest:
After he had arrived in Jerusalem, he [Egyptian king Ptolemy IV Philopator (c. 242 203 BNE)] offered sacrifice to the supreme God and made thank offerings and did what was fitting for the holy place. Then, upon entering the place and being impressed by its excellence and its beauty, he marveled at the good order of the temple, and conceived a desire to enter the sanctuary. When they said that this was not permitted, because not even members of their own nation were allowed to enter, not even all of the priests, but only the high priest who was pre-eminent over all and he only once a year the king was by no means persuaded. Even after the law had been read to him, he did not cease to maintain that he ought to enter, saying, Even if those men are deprived of this honor, I ought not to be. And he inquired why, when he entered every other temple, no one there had stopped him (3 Macc 1:912).
4) The Apostles and early Church Fathers quoted predominantly from the Greek text of the Old Testament. Luke, for example, follows the Septuagint (Gen 10:24; 11:1213) when he gives his genealogy of Jesus by inserting Cainan (Lk 3:36) between Sala and Arphaxad. In the Masoretic text, Cainan is omitted.
5) From antiquity to the present day, the text of the Septuagint has been preserved almost intact, at least with regard to chronology.
6) The idea that the Jewish-Masoretic Tanakh is an infallible text of the original Old Testament is, obviously, erroneous. Theres enough evidence to the fact that the Jews had several versions of Tanakh with varying chronological data. For example, in the account from Adam through Noah, the Samaritan-Israelite Pentateuch is closer to the Jewish-Masoretic Tanakh, whereas in the partition from Arphaxad through Abraham it is closer to the chronology given in the Septuagint. This indicates an evolutionary accumulation of discrepancies over a long period of time.
7) Accumulation of errors in the Tanakh continued throughout the1st century NE. The Jewish historian Josephus Flavius in his famous book provides the chronological data in the Bible which contains further discrepancies (see Judean Antiquities).
8) The belief in the infallibility of the Jewish-Masoretic Tanakh faded away altogether after the ancient Jewish manuscripts of Qumran had been unearthed in 1947. These manuscripts reflect a whole range of chronological and textual traditions. Based on the paleographic data, external evidence, and the radiocarbon analysis, the main body of these manuscripts date between 250 BNE to 68 NE.
9) The finalization of chronology in the Jewish Tanakh occurred, most likely, around the 2nd century NE. This process must have been caused by historical circumstances, such as the destruction of the Jewish Temple, and the Roman invasion of Judea in 70 NE. Scattered throughout the world, the Jews must have been motivated to start thinking about preserving the uniformity of their religious texts. The fixed Jewish-Masoretic text of Tanakh was first translated into a foreign language in Syria at the end of the 2nd century NE. This translation was later called Peshitta. After some time, in the 4th century NE, the Jewish-Masoretic Tanakh was translated by into Latin by Jerome of Stridon; this translation was termed the Vulgate.
10) The fixed text of the Jewish-Masoretic Tanakh is not identical across various manuscripts and contains multiple discrepancies.
11) The much shorter chronology of the Jewish Tanakh contradicts the current data obtained through independent dating methods. For example, according to the Jewish tradition, the conquest of the Babylonian Empire by Cyrus II happened in 370 BNE (year 3390 from the foundation of the world in the Jewish calendar). But the scientific dating places this event in 539 BNE.
Based on the above considerations, it seems reasonable to use the dates and numbers of the Septuagint as the source for recreating the Old Testament chronology.
The brief research given below is not meant to demonstrate the whole range of the Old Testament datings. Its main purpose is to indicate the general duration of the described events. Thats why only key dates have been included. Let us first note that the period from the creation of the world to the beginning of the new era was 5550 years. So for the sake of convenience, the calculated dates are given in a twofold format: first, the dates from Adam, then the astronomical dates in NE (in parentheses; -5549 NE corresponds to 5550 BNE and so on).
1 (-5549). Creation of Adam and Eve
So God created man in his own image, in the image of God created he him; male and female created he them And the evening and the morning were the sixth day (Gen 1:27, 31; compare Gen 2:725).
And Adam called his wifes name Eve; because she was the mother of all living (Gen 3:20).
The tradition holds that the first man and woman, Adam and Eve, were created on the sixth days of the 1st year. It is believed that this day was Friday.
231 (-5319). The birth of Seth
And Adam lived an 230 years, and begat a son in his own likeness, after his image; and called his name Seth (Gen 5:3).
1+230=231
436 (-5114). The birth of Enos
And Seth lived an 205 years, and begat Enos (Gen 5:6).
231+205=436
626 (-4924). The birth of Cainan
And Enos lived 190 years, and begat Cainan (Gen 5:9).
436+190=626
796 (-4754). The birth of Mahalaleel
And Cainan lived 170 years, and begat Mahalaleel (Gen 5:12).
626+170=796
961 (-4589). The birth of Jared
And Mahalaleel lived 165 years, and begat Jared (Gen 5:15).
796+165=961
1123 (-4427). The birth of Enoch
And Jared lived an 162 years, and he begat Enoch (Gen 5:18).
961+162=1123
1288 (-4262). The birth of Methuselah
And Enoch lived 165 years, and begat Methuselah (Gen 5:21).
1123+165=1288
1475 (-4075). The birth of Lamech
And Methuselah lived an 187 years, and begat Lamech (Gen 5:25).
1288+187=1475
1663 (-3887). The birth of Noah
And Lamech lived an 188 years, and begat a son: And he called his name Noah (Gen 5:2829).
1475+188=1663
2163 (-3387). The birth of Sim, Ham, and Japheth
And Noah was 500 years old: and Noah begat Shem, Ham, and Japheth (Gen 5:32).
1663+500=2163
2263 (-3287). The Great Flood
And Noah was 600 years old when the flood of waters was upon the earth (Gen 7:6).
The Flood happened 100 years after the birth of Sim, Ham and Japheth.
2163+100=2263
2265 (-3285). The birth of Arphaxad
Shem was an hundred <and two> years old, and begat Arphaxad 2 years after the flood (Gen 11:10).
The conjecture <and two> eliminates the contradiction between Gen 5:32, Gen 7:6 and Gen 11:10. This numeral was probably lost in the process of copying the manuscript long before the Septuagint was created. It is also absent in the Jewish-Masoretic Torah.