“There was in the days of Herod, the king of Judea, a certain priest named Zacharias, of the division of Abijah.” (Luke 1:5 NKJV)
• Each priestly course was one week in duration: “The Levites and all Judah did according to all that Jehoiada the priest commanded. And each man took his men who were to be on duty on the Sabbath, with those who were going off duty on the Sabbath; for Jehoiada the priest had not dismissed the divisions” (2 Chronicles 23:8 NKJV)
• The servants of the kings house, along with the priests, appear to have begun their week of service on the Sabbath, rather than on the first day of the week: “One third of you, who come in on the sabbath and keep watch over the king’s house” (2 Kings 11:5 NASU)
• The Keil & Delitzsch Commentary states, “Of these twenty-four classes, each one had to perform the service during a week in order … from Sabbath to Sabbath.” (1 Chronicles 24:19 footnote Carl Friedrich Keil and Franz Delitzsch, Commentary on the Old Testament (Peabody, MA: Hendrickson, 1996)
• The course of Abijah was the EIGHTH course selected: “Now the first lot came out for Jehoiarib … the eighth for Abijah … the twenty-fourth to Maaziah” (1 Chronicles 24:7-18 NASU)
• The McClintock and Strong Encyclopedia states regarding the Jewish Calendar, “The year begins in autumn as to the civil year, and in the spring as to the sacred year.” (“Calendar, Jewish” McClintock and Strong Encyclopedia)
• The New Unger’s Bible Dictionary indicates that Abijah was “one of the descendants of Eleazar, the son of Aaron, and chief of one of the twenty-four divisions or orders into which the whole body of the priesthood was divided by David” (“Abijah” The New Unger’s Bible Dictionary)
• The courses were determined by lot: “They divided them impartially by drawing lots” (1 Chronicles 24:5 NIV) It may be that the lot first selected the order of the 16 descendants of Eleazar, followed by the descendants of Ithamar. If so, then the course of Abijah listed in the first 16 groups belongs to the descendants of Eleazar. The Keil and Delitzsch Commentary on 1 Chronicles 24:6-18 states “These words would much rather suggest that a lot for Eleazar alternated with the drawing of one for Ithamar, until the eight heads of Ithamar's family had been drawn, when, of course, the remaining eight lots of Eleazar must be drawn one after the other. We cannot, however, come to any certain judgment on the matter, for the words are so obscure as to be unintelligible even to the old translators.” (1 Chronicles 24:6-18 Carl Friedrich Keil and Franz Delitzsch, Commentary on the Old Testament, vol. 3 (Peabody, MA: Hendrickson, 1996), 550)
• However, some scholars believe that the sequence of the priestly courses alternated between the descendants of Eleazar and the descendants of Ithamar: Clark’s Peoples Commentary states, “Meyer suggests that the reckoning must be made backward from the destruction of the temple which took place on the tenth of Ab - that is, July 15th, A. D. 70 - when the first course, that of Jehoiarib, was in waiting. Thus reckoning on the supposition that the several classes had during all that time performed their service regularly and in succession, we arrive at the latter part of March, B. C. 6 of the common era, as the time of Zachariah’s service.” (Luke 1:5 “The Gospel of Luke: A Popular Commentary upon a Critical Basis, Especially Designed for Pastors and Sunday Schools. Clark’s Peoples Commentary” by G. W. Clark)
• G. R. Bliss wrote, “Abijah stood first in the eighth of them, and as the date of the destruction of the temple (A. D. 70) is known, and the course of the priests (that of Joarib) then officiating is known, it has been supposed that something definite could be concluded by reckoning backward from that date, as to the week here intended, then, as to the time of John’s birth, then, as to the year, the month, the week, and even the day, of the birth of Jesus.” (Luke 1:5 George R. Bliss, Commentary on the Gospel of Luke (Philadelphia: American Baptist Publication Society, 1884), 23)
The cycle for the 24 courses was repeated TWICE each year, with the first cycle beginning in the first month and the second cycle beginning in the seventh month.
• The article “Christmas – Was Jesus really born December 25th?” states, “By means of this arrangement, after the 24th course was completed, the cycle of courses would repeat, so that in a given year each group of priests would serve in the Temple twice per year” (“Christmas – Was Jesus really born December 25th?”, accessed 4/25/2012 at http://www.hebrew4christians.net/Articles/Christmas/christmas.html)
Scripture only states that this was the “course of Abijah” but is silent as to whether this was the first or the second cycle for the priestly courses.
If this was the FIRST course of Abijah, then Zechariah served the 10th week of the year:
The article “Christmas – Was Jesus really born December 25th?” states, “The Jewish calendar begins in the Spring (Nisan), so the first course of priests (Jehoiarib) would serve for seven days … The third week would be the festival of Passover, when all priests would be present for service, so the schedule would resume with the third course of priests (Harim) on the fourth week. By the tenth week, since both Passover and Shavu’ot [Pentecost] had occurred, the 8th course of Abia (Abijah) would be called for temple service … The cycle of service began on the first Shabbat of Nisan but both Passover and Shavu’ot require all priestly courses to serve, the actual time the 8th course would serve would be during the 10th week of the year. This places Zacharias' service in the Temple as beginning on the second Sabbath of the month of Sivan (May/June).” (“Christmas – Was Jesus really born December 25th?”, accessed 4/25/2012 at http://www.hebrew4christians.net/Articles/Christmas/christmas.html)
The interval between Zechariah completing his service during the course of Abijah and when Elizabeth became pregnant is not specifically stated; only that it was “after these days”: “After these days Elizabeth his wife became pregnant, and she kept herself in seclusion for five months” (Luke 1:24 NASU) Yet it does appear that Elizabeth became pregnant IMMEDIATELY with John who became the messenger of the Lord.
“I am the voice of one crying out in the wilderness, ‘Make straight the way of the Lord,’… John answered them, ‘I baptize with water, but among you stands one you do not know, even he who comes after me, the strap of whose sandal I am not worthy to untie.’” (John 1:23-27 ESV)