Jews in these regions used Seleucid Era dating (also known as the "Anno Graecorum (AG)" or the "Era of Contracts") as the primary method for calculating the calendar year. Jacob then put this question: How do we know that our Era [of Documents] is connected with the Kingdom of Greece at all?
In the course of their studies, men such as Tatian of Antioch (flourished in 180), Clement of Alexandria (died before 215), Hippolytus of Rome (died in 235), Sextus Julius Africanus of Jerusalem (died after 240), Eusebius of Caesarea in Palestine (260-340), and Pseudo-Justin frequently quoted their predecessors, the Graeco-Jewish biblical chronographers of the Hellenistic period, thereby allowing discernment of more distant scholarship.
They can be found in the Apology to Autolycus (Apologia ad Autolycum) by Theophilus (AD 115-181), the sixth bishop of Antioch, His chronology begins with the biblical first man Adam through to emperor Marcus Aurelius, in whose reign Theophilus lived.
The chronology puts the creation of the world at about 5529 BC: "All the years from the creation of the world amount to a total of 5,698 years." Dr.
It was the first day of the year in the medieval Julian calendar and the nominal vernal equinox (it had been the actual equinox at the time when the Julian calendar was originally designed).
Considering that Christ was conceived at that date turned March 25 into the Feast of the Annunciation which had to be followed, nine months later, by the celebration of the birth of Christ, Christmas, on December 25.