Knowing the age of John relative to Jesus, helps us to identify the time of the Savior’s birth. Luke indicates that Elisabeth concealed her pregnancy five full months (Lk. 1:24). Luke then reports it was during the sixth month of Elisabeth’s pregnancy that Gabriel appeared to Mary with word that she would conceive Christ (Lk. 1:26). The phrase “in the sixth month” signifies that Elisabeth had completed five months and was fulfilling her sixth month when Gabriel brought tidings of Christ’s coming birth. We are not told how many weeks into Elisabeth’s sixth month she was when the announcement came or when Mary actually conceived. We only know that sometime during Elisabeth’s sixth month Gabriel made his announcement to Mary.
Next, Luke tells us that Mary, pregnant with the Christ child, visited Elisabeth and abode with her “about three months” and then “returned to her own house” (Lk. 1:56). The phrase “about” here means “almost” or “just about.” We see this in relation to Abraham, whom Paul was “about an hundred” when he received the promise of Isaac’s birth, but by consulting Genesis, we find he was actualy only ninety-nine (Rom. 4:19; Gen. 17:17, 24; 21:5). Thus, Mary’s stay with Elisabeth was just short of three full months. The scripture then states “Now Elisabeth’s full time came that she should be delivered; and she brought forth a son” (Lk. 1:57). Therefore, we have Luke’s express testimony that Elisabeth arrived at full term following Mary’s visit. Since Mary was pregnant when she first came to visit Elisabeth, stay almost three months, and Elisabeth came to full term just after Mary departed, the natural inference is that there was fully six months difference between John and Jesus.
Based upon a reconstruction of the priestly courses, if Zechariah was serving in the second ministration of the course of Abijah in 3 BC when he received word that Elisabeth would conceive, and if she conceived the first month Zechariah returned home, a 38-week gestation would place John’s birth the week of Tammuz 20-26 (June 20-26), 2 B.C. Six months is 26 weeks. Twenty-six weeks from John’s birth brings us to Tebet 26-Shebat 3, which answers to the week of December 21-27.