While Christians in the West (Catholic and Protestant) celebrate the birthday of Christ every year on the twenty-fifth of December, no one knows for sure what exact day the birth occurred. There is no birth certificate. We have no references or citations in the Bible about the Apostles having birthday parties for Jesus, and the calendar day of His birth is never mentioned. That He was born is accepted as fact. What day of what month is not specified in any biblical or historical record. The Bible tells us Jesus was born of Mary in the town of Bethlehem. Later, the holy family (Jesus, Mary, and Joseph) fled into Egypt to escape the slaughter of male infants imposed by King Herod. After Herod’s death, the family settled in Nazareth, where Joseph worked as a carpenter.
After Jesus’ death and resurrection came three hundred years of Roman persecution (54–305 AD) by Emperors Nero, Domitian, Trajan, Marcus Aurelius, Septimius Severus, Maximus, Decius, Valerian, Aurelian, and Diocletian, which made Christianity an outlawed and ghettoized religion. Only after the Emperor Constantine issued the Edict of Milan in 315 AD, granting legal protection for Christians and their religion, did people begin to ask when they could celebrate the birthday of the Savior.
Without knowing the actual day, there are two ways to determine a day on the calendar for the annual birthday of Christ. One school of thought maintains that the Annunciation (when the Archangel Gabriel appeared to the Virgin Mary and announced that she was to be the mother of the Savior), already established in antiquity as March 25, would also have been the day Jesus was conceived in the womb of His mother. Luke 1:36 tells us that the same day of the Annunciation is also the six-month anniversary of the conception of Saint John the Baptist in the womb of his mother, Saint Elizabeth. Luke 1:56–57 tells us that after three months, Mary returns home when her cousin gives birth. If the Annunciation took place on March 25, then the birth of John the Baptist must be three months later, and the Church does in fact celebrate the birth of John on June 24. Mary would have been with child since March 25, and nine months from that date brings us to December 25.
If the actual day of the Annunciation or the Visitation (when Mary visited Elizabeth) is not known, someone like Saint Augustine would propose that it was based on the solar calendar of the Roman Empire. Rather than adapting a pagan feast day of the sun god as is often suggested, other scholars use the following line of reasoning: without a firm date to use, Scripture helps by using analogies. Jesus said in John 8:12 “I am the Light of the World.” John the Baptist, the cousin of Jesus and son of Elizabeth, said in John 3:30 “I must decrease, He must increase.” Using those two biblical passages, Christians then looked at when the shortest and the longest days of the year occurred—the summer and winter solstices.
The longest day occurs in mid-June and the shortest day occurs in mid-December. On the day after the summer solstice, the amount of daylight decreases every day until we reach the shortest day of the year. The day after the winter solstice, the amount of daylight increases until we return to the longest day. The day when the hours of light begin to increase would be designated as the birthday of Christ (“I am the Light of the World”) and the day when the hours of light began to decrease would be the designated as the birthday of John the Baptist (“I must decrease, He must increase”). There are exactly six months between the birth of John the Baptist and the birth of Christ as told in Luke’s Gospel, and there are exactly six months between the summer and winter solstices. Hence, the day when light decreases becomes the birth of John on June 24, and the day when the light increases becomes the birth of Jesus on December 25. It may not be as precise and as accurate as astronomers and chronologists might prefer, but it works.