Determining the precise dates of the births of John the Baptist and Jesus Christ has been a longstanding topic of biblical scholarship and debate. While the exact dates are not definitively stated in scripture, careful examination of the biblical accounts along with historical context allows us to construct a reasonable chronological timeline.

Let us begin with the fixed date of Jesus's birth, which we hold was about February 28 in the year 4 BCE (about the time when shepherds routinely returned from their winter break and yet before Herod would likely have broken the Jewish belief in travel to Jerusalem during Passover, April 11-12 of that year). Working backwards from this date, and assuming a normal gestational period of 38-40 weeks, we can estimate that Jesus's conception by the Virgin Mary occurred around early June of 5 BCE when Mary was likely around 14-15 years old.

Six months before the birth of Jesus, John the Baptist was born to the elderly couple Zacharias and Elizabeth (Luke 1:26,36). Calculating his conception date is more complex given Elizabeth's advanced maternal age, which may have extended her gestational period beyond the typical 38-40 weeks. Assuming a longer gestation of 42-44 weeks, John was likely conceived in the November timeframe of 6 BCE.

This lines up with the biblical detail that Zacharias was a priest serving in the course of Abijah at the Jerusalem temple prior to returning home and conceiving John with his wife Elizabeth (Luke 1:5,23-24). Factoring in several days of travel time for the elderly Zacharias, the course of Abijah he served would have been in the October 6 BCE period, before conceiving John in early-to-mid November 6 BCE.

Around early June of 5 BCE, when Mary had just conceived Jesus, she visits her relative Elizabeth who was already six months pregnant with John (Luke 1:39-45). This timing corroborates our calculated conception dates for both John (November 6 BCE) and Jesus (June 5 BCE).

As for the birth narrative itself, the census decreed by Herod which prompted Joseph and the pregnant Mary to travel to Bethlehem was likely timed to avoid conflicting with Passover when all Jewish males were required to be in Jerusalem. Herod possibly set uncomfortable late February travel deadlines to register in Bethlehem, but would have made concessions for Passover observances in April of 4 BCE, a few weeks after Jesus's estimated February 28 birth.

In summary, based on the biblical data:

• Jesus was likely conceived around early June of 5 BCE.
• John the Baptist was likely conceived in early-to-mid November of 6 BCE.
• Jesus was born on very near February 28, 4 BCE.
• John the Baptist was born six months earlier on or very near September 1st, 5 BCE.
• Key events like the course of Abijah, Mary's visit to Elizabeth, and Herod's census align with this chronology.

While we cannot pin down the exact dates with absolute certainty (as there could have been cloudy weather which would have reset the appearance of the new moon), this composite timeline harmonizes the various scriptural details into a cohesive chronological sequence for two of the most pivotal births in human history.

Or, if one believes that God would have foreknown and allowed Jesus to be dedicated at the full moon, then we can rather simply set the date of the birth of Jesus as February 28, 4 BCE (Gregorian).