It comes as quite a shock to many people to discover that Jesus was not born on December 25th, at the end of the year 1BC.
Our current system of numbering the years can be traced back to a Roman monk by the name of Dionysius Exiguus (Denis the Little). He was commissioned by Pope John I in 525 to prepare a standard calendar for the Western Church. Up to that point, calendar dating had been reckoned from the foundation of Rome and years were known as AUC (Ab Urbe Condita, i.e. from the foundation of the city (Rome)); sometimes referred to as YOR (Years of Rome).
Dionysius preferred a calendar that was reckoned from the birth of Christ and not a persecutor of the church and (wrongly, as it happens) calculated the start of the Christian era as from 1st January 754 AUC. Based on the traditional belief that Christ had been born on 25th December of the preceding year, Dionysius labelled 754 AUC as AD 1 and the previous year as 1 BC. We now know that Dionysius was out by a few years but his calculations have stuck.
There are two time references points given to us in the Scriptures, to help us determine the date of Christ’s birth.
i. The latest possible point in time
Scripture clearly tells us that Christ was born during the reign of Herod the Great (Matthew 2:1, 7, 16, 19).
We know from the Jewish historian Josephus that Herod died, at the age of 70, 37 years after being declared king by the Romans, and that happened 714 AUC, so his death must have occurred in 750 – 751 AUC, since Josephus always computes a year as from Nisan to Nisan.
Josephus also records that just following Herod’s death it was the celebration of the Passover. In 750 AUC/4 BC that would have occurred on April 7th of 4 BC, so Herod’s death had to happen before 7 April 4 BC.
Josephus mentions an eclipse of the moon which occurred shortly before Herod died. This eclipse is the only one alluded to by Josephus and, as the Lord Jesus was born while Herod was still living (Matthew 2:1-6), it thus serves to fix with “absolute” certainty the time after which the birth of Jesus could not have taken place. Astronomical calculations locate a partial eclipse of the moon March 12/13 in the year of Rome 750; no eclipse occurred the following year that was visible in Palestine.
So Christ must have been born prior to the death of Herod the Great, which happened sometime in the weeks or days prior to 7 April 4 BC. There is, however, considerable speculation as to how much before 4 BC Christ was born, so we need to consider the other time reference point.
ii. The earliest possible point in time
According to Luke 2:1-2, the birth of Christ happened at the time connected with a census decreed by Caesar Augustus during the governorship of Quirinius.
According to the Roman historian Tacitus, Publius Sulpicius Quirinius was elected Legatus, or governor of Syria, around 7 BC. During this time he oversaw in his region the empire-wide census decreed by Caesar Augustus. There is some evidence that the census was not actually carried out in Palestine until two to four years after it was ordered, perhaps because of political tensions between Herod and his superiors in Rome.
Given the above, this makes it as certain as we can be, that Christ was born somewhere between 6 BC and 7 April 4 BC
But can we be even more precise as to the date or time of year?
The traditional date of 25th December can be traced back as far as the testimony of Hippolytus around the beginning of the 3rd century. It is quite possible that the date was chosen to coincide with the Roman pagan festival of Saturnalia which honoured the birth of the Babylonian ‘Queen of Heaven’, Semiramis (see Jeremiah 7:18; 44:15-30). In AD 354, Bishop Liberius of Rome ordered the people to celebrate it on December 25 and it was officially accepted by the church fathers in AD 440.
As we shall see when we consider the events immediately after the birth of Christ, it would appear that Herod, who died sometime shortly before 7 April 4 BC, died within 40 days of the nativity, so lending credence to the supposition that Christ was born in or around March, in the year 4 BC.