Have you ever wondered if Jesus was actually born on December 25? Or why some countries celebrate Christmas in January? Or how long Christians have been celebrating on December 25? Does it matter? A skeptic could argue that if Christians don’t know the birthdate of the founder of the faith, then maybe other tenets of Christianity or the Bible itself may not stand up to scrutiny.
Identifying Birthdates Is Not So Straightforward Today, the birthday is one of the most basic pieces of information that identifies a person. But it wasn’t so basic as recently as a century ago. When my father moved from a small village in China into the Western world, he knew his birthdate only in the lunar calendar, which is based on the cycles of the Moon. Even today, his identification card issued by the government shows only his birth year, with no month or day. He still prefers that his family celebrate his birthday in the lunar calendar. As a result, his children remember his birthdate only in the lunar calendar and we look up his birthdate in the Western calendar every year. This process can lead to confusion—and my father was born within the past 100 years!
Jesus was born over 2,000 years ago into the Jewish culture, which also used a lunar calendar. The Roman Empire at the time, however, adopted the Julian calendar. Today’s Western calendar, the Gregorian calendar, was adopted only within the past few hundred years. Thus, I can imagine confusion about “converting” Jesus’s birthdate twice: (1) from a lunar calendar to the Julian calendar; and (2) from the Julian calendar to the Gregorian calendar. Although this second conversion should be straightforward, the differing adoption dates of different countries have nevertheless caused great confusion.
Julian Calendar In 46 BC, Julius Caesar reformed the calendar system based on the perceived cycles of the Sun. The Julian calendar included a leap year every four years, resulting in an average of 365.25 days in a year. However, because Earth orbits the Sun in 365.24219 days, a Julian year was slightly longer than it should be.1 This difference of 0.00781 days in a year might not mean much initially, but it accumulated to 7.81 days after 1,000 years. Astronomical events like the equinoxes and solstices drifted on the Julian calendar. For example, with Easter tied to the first full moon after the spring equinox, it drifted slowly into early March.
Gregorian Calendar Recognizing this drifting problem, Pope Gregory XIII modified the Julian calendar by proposing two changes in 1582. First, 10 days would be skipped when switching from the Julian calendar to the Gregorian calendar. This skipping would account for the drifting caused by the Julian calendar since the third century. Second, beginning in 1582, the Gregorian calendar would include a leap year every four years, like the Julian calendar. But it would not have a leap year for the years ending in 00, unless divisible by 400. Therefore, 1700, 1800, 1900, and 2100 would not be leap years, but 1600 and 2000 would be leap years. Effectively, there are 365.2425 days in a Gregorian year on average, making it a much better approximation of the number of days Earth orbits the Sun.
Drifting of Christmas Day Here comes the confusion. Only certain countries (including France, Italy, Poland, Portugal, and Spain) converted to the Gregorian calendar in 1582. The later a country converted, the more days it would have to skip to account for the drifting difference. For example, when the United States, United Kingdom, and Canada converted in 1752, they had to skip 11 days. To them, the day after September 2, 1752 (the day the Gregorian calendar was adopted), was September 14, 1752. Bulgaria, Estonia, Russia, Greece, and Turkey skipped 13 days when they converted after 1900.2
Each of these countries consistently celebrated Christmas before and after the conversion: on December 25 of the Julian calendar before its conversion, and on December 25 of the Gregorian calendar after its conversion. However, to the people who know only the Gregorian calendar, the converting country would appear to have moved its Christmas from January 5, 6, or 7 to December 25.
The timing differences are confusing even now. Churches in a small number of countries still use the Julian calendar today. They celebrate Christmas on December 25 of the Julian calendar, but to the world using the Gregorian calendar, they appear to celebrate Christmas on January 7. The table below shows how Christmas Day of the Julian calendar drifts on the Gregorian calendar over centuries.
Julian Calendar
Gregorian Calendar
Days Drifted
Dec 25, 1582
Jan 4, 1583
10
Dec 25, 1600
Jan 4, 1601
10
Dec 25, 1700
Jan 5, 1701
11
Dec 25, 1800
Jan 6, 1801
12
Dec 25, 1900
Jan 7, 1901
13
Dec 25, 2000
Jan 7, 2001
13
Dec 25, 2100
Jan 8, 2101
14
December 25 since the Second Century Therefore, since 1582, Christians have been consistent when celebrating the birth of Jesus on December 25. What about the years before 1582? Here are some ancient accounts—starting in the second century—that recorded Jesus’s birthday on December 25:3
The early church father Irenaeus, who lived from 130 to 202 AD, wrote in the second century that Jesus was born on December 25.4 Irenaeus was a student of Polycarp, who was a disciple of the apostle John, who was closely affiliated with Jesus’s mother (John 19:26–27). To me, this seems to be the most reliable source.
The historian Sextus Julius Africanus (160 to 240 AD) recorded in the year 221 AD that Jesus was conceived on March 25, extrapolating forward nine months that Jesus was born on December 25.5
The early church father Hippolytus (170 to 236 AD) wrote that Jesus was born on December 25.6
These ancient accounts demonstrate that December 25 was recorded as Jesus’s birthday as early as the second century. Was Jesus’s birthday initially remembered in the Jewish lunar calendar and subsequently converted to the Julian calendar? Probably. Was it converted accurately before the invention of paper or the smartphone? We don’t know. But these very early manuscripts suggest that the birth of Jesus probably occurred on or around December 25.
Did Christmas Replace a Pagan Festival? One of the most common criticisms of December 25 as the plausible date for the birth of Jesus was that this date was originally a Roman festival of Saturnalia honoring the god Saturn. After Christianity was legalized, according to this myth, Christians chose December 25 to replace this festival.
However, Saturnalia was celebrated from December 17 to 23, not on December 25. There was no replacement. Furthermore, when Christians of the second century recorded December 25 as Jesus’s birthday, they were still being persecuted by the Roman emperor and sought to distance themselves from the imperial cult. Finally, according to historians, the idea of Christians choosing Christmas to replace a festival first appeared in the twelfth century—10 centuries after the historical records. This idea was then popularized by new studies of comparative religions in the eighteenth and nineteenth centuries.7
Ironically, the conversion of countries from the Julian calendar to the Gregorian calendar appears to support this myth of replacing a pagan festival with Christmas. To people who are not aware of the calendar drifting problem and the calendar conversion, it seems that countries in the world moved Christmas from January to December 25 over centuries, thus allegedly supporting this myth.
Shepherding in December? Skeptics argue that December would have been too cold for shepherds living out in the fields as recorded in Luke 2:8. However, ancient shepherding in areas much colder than Bethlehem, such as the Himalayas and Mongolia, was not uncommon. Furthermore, Bethlehem is relatively warm in December, with a high of 14°C (57°F) and a low of 8°C (46°F). One can still see shepherding near Bethlehem in December today.
Significance of Christ’s Birth Ancient manuscripts in the second century recorded Jesus’s birthday as occurring on December 25. These manuscripts were written when Christians were persecuted by the Roman Empire and before Christianity was legalized in the fourth century. Christians have been consistently celebrating the birth of Jesus on December 25 until today, though the use of different calendars might have caused some confusion. While nobody knows for sure what date Jesus was born, December 25 remains the most plausible date after two conversions involving three calendar systems.
Not knowing the exact date of Jesus’s birth (scholars debate the year as probably between 8 and 2 BC) should cause no loss of confidence in the truth of the events surrounding his birth. Just as nobody in my family doubts that my father was born in the last century, Christians have no reason to doubt that Jesus was born under the reign of Caesar Augustus. The Gospel of Luke records specific details of his birth, but Scripture doesn’t provide a date. Yet the Bible provides ample evidence to demonstrate why Jesus was born, lived, died, and was raised from the dead. He accomplished atonement for sin on behalf of those who place their trust in him.
Titus Kennedy, Excavating the Evidence for Jesus: The Archaeology and History of Christ and the Gospels (Eugene, Oregon: Harvest House Publishers, 2022).
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