Dating service temple
If we bracket out for the moment the three weeks of the year when all twenty-four courses were on duty, we find by this approach that the course of Abijah would have come on duty during only one week that would yield a Christmas date within our established parameters.
Presumably, within a week or two of his return from Jerusalem, John was conceived.
The key, therefore, is to narrow down the dates on which Zechariah would have been serving at the temple.
We know from Josephus that the first division, the division of Jehoiarib, was on duty when Jerusalem was besieged during the first week of April, AD 70 (Nisan 1-8, AM 3830).
When then would the division of Abijah (the eighth division) have been serving ca. If the courses served in the same weeks of every year, this would have the Abijah division coming on duty Assuming John was conceived within the week after Zechariah returned from his temple service, the May-June date would yield a date for the birth of Jesus in the fall; if the September-October date is preferred, the result is Jesus being born in winter.
In theory, if one could pinpoint the day on which Zechariah and Elizabeth conceived John the Baptist, one could extrapolate an approximate date of Jesus’ birth.
Elizabeth was “in her sixth month” of pregnancy when the angel Gabriel came to Mary.
In other words, either of the prevailing theories can be supported by this method of calculation!
If, however, the divisions drifted through the year to keep strict time with the count of weeks—and if this week count was not interrupted by leap years—then we can calculate backward from Jehoiarib’s service the first week of April in AD 70.