Some ancient Christians thought so. In fact, other dates were considered as well.
A heretical Christian group (known as the Alogi) located in Asia Minor (modern Turkey) apparently dated Jesus’s birth on (what would for us be) either June 20 or May 21 (depending on the reading) in the year 9 CE. An unrelated group of Christian Gnostics in Egypt (followers of the Gnostic teacher Basilides) gave a similar date for Jesus’s birth: May 20. They also believed that Jesus’s baptism occurred on this same date exactly thirty years later.
Early Christian theologian and historian, Epiphanius of Salamis (315-403 CE), claimed that the May date was actually the date of Jesus’s conception rather than his actual birth. Was this what the heretical groups noted above originally intended? Epiphanius wrote that the actual date of Jesus’s birth was on January 6, a winter solstice date (when one of the Earth’s poles has its maximum tilt away from the Sun), and he cites a number of traditions to prove it. This date became known as Epiphany, which comes from the Greek word for “the appearing” as it is used in 2 Timothy 1:9-10:
He is the one who saved us and called us with a holy calling, not based on our works but on his own purpose and grace, granted to us in Christ Jesus before time began, but now made visible through the appearing (epiphaneias) of our Savior Christ Jesus. (1 Tim. 1:9-10 NET)
Thus, many early Christians thought that January 6 was the date that Jesus, the glory of God, appeared on earth and the same date that, thirty years later, the Spirit appeared to Jesus as a dove as it entered him during his baptism.
Another tradition understood that Mary’s pregnancy lasted “ten months less fourteen days and eight hours,” or, put another way, “nine months plus fifteen days and four hours.” Those Christians, counting backward from Jesus’s presumed birthdate of January 6, derived the date of Mary’s conception as March 20. Coincidentally, that would be the same date that they also believed Jesus was crucified. Therefore, some Christians claimed that Jesus both came into the womb of an earthly, human woman and left the earth as a human being on March 20.
Scholar Jack Finegan notes that the birth date of January 6 may have been chosen to supplant a popular, pagan religious ceremony dedicated to the goddess Kore that was held on that date in such locales as Egypt and Arabia. On the night of January 5 and the morning of January 6…
“The participants stay awake all night…making music to the idol with songs and flutes. In the early morning at cockcrow they descend by torchlight to a subterranean shrine and bring forth a wooden image, marked with the sign of a cross and a star of gold on hands, knees, and head. This image they carry in procession to musical accompaniment, and then return it to the crypt. They explain the meaning of the ceremony to the effect that in this hour this day Kore, the virgin, gave birth to the Aion.” (Handbook of Biblical Chronology, pg. 325)
December 25 was also a winter solstice date as well as the date of another pagan festival. It has equal claims on early tradition as being the date of Jesus’s birth, deriving from at least the second or third century. Unfortunately, December 25 has no greater claim to authenticity than January 6. Nevertheless, fourth-century theologian John Chrysostom defended this date by claiming that, since John the Baptist, in his view, was conceived between September 25 and October 1 (the Feast of Tabernacles), then Mary would have conceived Jesus six months later (Luke 1:26) in April. Nine months after that (counting inclusively), Jesus was born on December 25.
As many readers will already know, December 25 was the date of the pagan festival of Sol Invictus, the “Invincible Sun.” As Finegan points out:
“The cult of Deus Sol Invictus was still at its height in the time of Constantine and the portrait of the sun god was on the coins of the emperor, but with his rise to sole rule of the empire (A.D. 323-337) Constantine was free to accept Christianity openly. Thereafter his coins and inscriptions were no longer offensive to Christians and Dec 25 was freely the birthday of Christ, as attested in the Roman city calendar in A.D. 336.” (pg. 328)
Regardless of the date chosen, ancient Christians seemed to agree that Jesus was conceived in the spring (shepherds abiding in the fields?) and born in the mid-winter. Whether either of these choices are historically accurate is debatable. Each has a 1/365 chance of being right! The Feast of Epiphany is still celebrated in Christianity either as the day of the visitation of the Magi to Jesus’s crib (Western tradition) or the date on which Jesus was baptized (Eastern tradition). While most churches continue to celebrate Epiphany on January 6, others do so on January 1 or even January 19. Some call it Twelfth Night, Three Kings’ Day, or Little Christmas. Whether or not Jesus was born on this date, it remains a prominent festival in the Christian calendar.