The course of Abijah is the eighth course (1Chron. 24:10), which serves the tenth week during the former rain portion of the year (this is because during Passover and Shavuot (Pentecost) all of the priests serve together Dt. 16:16.   

Zechariah had his vision while serving in the course of Abijah in the tenth week (It will become apparent that he was serving his first course not his second as the timing will show as we progress).  Thus Zechariah's vision took place during the 10th week of the year (The religious year beginning at Nisan/Abib around 14 days before Passover).  We must add two additional weeks before Yochanon (John) could be conceived, due to the purity laws (Lev. 12:5; 15:19, 25).  So Yochanon was conceived in the 12th week of the year.  He was born about 40 weeks later during the 52nd week of the year (12 + 40 = 52) that brings us to Passover.  Thus Yochanon was born at Passover, the very time that Elijah was, according to Jewish tradition, supposed to appear.

Yeshua was conceived 6 months (about 25 weeks) after Yochanon's conception.  This means Yeshua was conceived around the 37th week around Chanukah.  This would mean the light of the world was conceived during the festival of lights.

Yeshua was born 40 weeks later (around week 77 that is week 25 of the following year) this brings us to the time of the fall feasts.

There are several clues that Yeshua was born at Sukkot:

1.  Bethlehem was "booked solid."  This would not have been due census which would have taken place over the period of a year. Every Jew was required to come to Jerusalem for Sukkot (Dt. 16:16) this would have over run Jerusalem as well as Bethlehem just five miles away.

2.  Yeshua was born in a stable.  The Hebrew word for "stable" is "sukkah" (as in Gen. 33:17) so it is likely that Yeshua was born in a Sukkah/booth.

3.  If Yeshua was born on the first day of Sukkot then he would have been circumcised on the "eighth great day" a festival following Sukkot.  This day was the original "Simchat Torah" (Rejoicing in the Torah), which is now held the following day in Rabbinic Judaism. So Yeshua would have entered the covenant on the day of "rejoicing in the Torah."

4.  When the angels appeared to the shepherds they made a statement which closely echoes the ancient Sukkot liturgy "...behold, we have come to declare to you glad tidings of great joy." (Lk. 2:10-11)

5.  Sukkot is symbolic of God dwelling in a "tabernacle" (body?) with us.

Now in Mt. 2:7-8, 16 Herod kills all the children two and under.  The fact that he killed such a wide range indicates that he did not know quite how long ago Messiah had been born.  Yeshua's parents fled to Egypt until they heard Herod was dead.  They were back in Bethlehem in time to perform Miriam's (Mary's) purification and Yeshua's dedication on the 4oth day after Yeshua's birth (as required by Torah) (Luke. 2:22-38.  By this time Herod had to be dead or they could not have come to the Temple in Jerusalem.  Herod had to have died during the 40 days between Yeshua's birth, and his dedication 40 days later.  Herod is known to have died in September of 4 B.C.E.  So Yeshua had to have born in the fall (this rules out that Zechariah could have been serving during Abijah's second course of the year, since that would place Yeshua's birth in the Spring and not allow for Herod's death during the 40 days after his birth in the fall).  This also tells us that the year of Yeshua's birth was 4 B.C.E.