When Was Jesus Born?

One might be inclined to think that when Jesus was born is obvious: on December 25, Christmas, in the year 0. And one might think his birth marked an epochal shift, after which the date is reckoned as ad (anno Domini, meaning “the year of our Lord” in medieval Latin—not “after death,” as some people think) and before which it is bc (“before Christ”). The truth is, no one really knows the year, or even the day, that the historical figure of Jesus was born.

Why the uncertainty? First, the calendar system in the widest use today was not fully in place at the time of Jesus’ birth. Second, the date of Jesus’ birth was not recorded with any degree of precision when it happened, and the Gospels provide piecemeal evidence. Third, Jesus’ birth date was not particularly important to the earliest writers on Christianity, and the date of December 25 was gradually identified by church leaders only in the 3rd and 4th centuries. Fourth, there is no year 0 in the calendar system most widely used today, which developed before the idea of zero arrived in Europe. The day of Jesus’ birth as December 25, the year he was born, and the calendar system now used across much of the world all developed gradually over the centuries after Jesus’ earthly life. Historians have made numerous attempts to estimate the date of Jesus’ birth on the basis of hints in the New Testament, but even their conclusions are tentative.

Textual evidence for Jesus’ birth year

Many historians and scholars of religion suggest, on the basis of evidence in the Gospels, that the historical figure of Jesus was likely born between 6 and 4 bc (or bce, “before the Common Era”). But the Gospels, written in the latter half of the 1st century ad (or ce, “Common Era”), provide conflicting and incomplete evidence for determining the year of Jesus’ birth. The Gospel of Matthew suggests that Jesus was born toward the end of the reign of Herod the Great, the Roman-appointed king of Judaea, which concluded with Herod’s death in 4 bce (Matthew 2). Matthew also records Herod’s attempt, after learning of Jesus’ birth, to kill all children under the age of two in Bethlehem. For many historians, this evidence is the most significant, and it establishes Jesus’ birth sometime in the range of 6–4 bce. Yet, that conclusion presumes St. Matthew’s historical accuracy, though his Gospel was likely written sometime in 70–80 ce—at least four decades after the Crucifixion, which was about 30 ce. Also, a few historians suggest that Herod died in 1, not 4, bce.

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Further complicating matters, according to the Gospel of Luke, Jesus was born at the time of a census conducted while Quirinius was governor of Syria (Luke 2). However, other evidence indicates that such a census occurred in 6–7 ce, which conflicts greatly with Matthew’s account. Plenty of scholastic ink has been spilled trying to explain this discrepancy. Some scholars have provided alternate readings of the Greek text of Luke (e.g., rendering it as “before Quirinius was governor”). Others have surmised that Quirinius served as governor at an earlier point in history when Herod was still alive, or that he conducted a census earlier as a ruler, but not officially as a governor, of Syria. Or else Luke somehow mixed up the date. The Gospel of Luke was probably written in 63–70 ce and possibly as late as 80—at least six decades after Jesus’ birth.

In addition, Luke indicates that St. John the Baptist—who was six months older than Jesus, according to Luke 1—began his ministry in the 15th year of the Roman emperor Tiberius, which would have been about 29 ce (Luke 3:1). Luke also notes that Jesus began his ministry soon thereafter, at the age of “about thirty” (Luke 3:23), which would make his birth year about 2 bce. Yet, Luke’s mention of “about thirty” leaves ample wiggle room. A number of other early Christian writers place Jesus’ birth at about 2 or 3 bce, but there is no consensus.

Why December 25 is now considered Jesus’ birthday

There is no precise evidence in the Gospels to indicate what time of year Jesus was born. Some commentators speculate that the date was in the early spring or fall, when, per Luke 2:8, the shepherds were in the fields. Groups of Gnostic Christians in Egypt in the early centuries ce proposed dates for Jesus’ birth on the Egyptian calendar that would correspond to May 20, April 19 and 20, and January 6 on the most widely used modern calendar. In many ancient Christian communities, January 6 came to be recognized and celebrated as the date of Jesus’ birth. Meanwhile, some early Christian scholars, combining elements from Roman religion and solar symbolism, chose March 25, the Roman spring equinox, as the date of the creation of the world, that of Jesus’ death, and, for some, that of his birth. Other writers averred that March 28, the fourth day of creation, when God created the Sun and the Moon, was Jesus’ birthday.

Then in 221 the early Christian historian Sextus Julius Africanus (c. 180–c. 250) became the first writer to indicate that December 25, now recognized as Christmas by most Christians, was the date of Jesus’ birth. This conclusion was based on his calculation that March 25 was the date of the Annunciation—the announcement by the angel Gabriel to the Virgin Mary that she would conceive a son by the power of the Holy Spirit. Africanus reasoned that the Annunciation coincided with Jesus’ conception in Mary’s womb and hence marked Jesus’ Incarnation. From that date, Africanus calculated a typical nine-month gestation period to arrive at December 25. The first recorded celebration of Christmas on December 25, observed with the approval of the church at Rome, occurred more than a century later, in 336, according to a manuscript dating to 354.

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There are other possible origins of the December 25 date that took hold in the 4th century in Western Christendom. In 3rd-century Rome it was popular to celebrate the winter solstice as the rebirth of the Unconquered Sun (Sol Invictus), on December 25. That was also reckoned to be the date of the birth of Mithra, a deity in Indo-Iranian mythology whose cult, Mithraism, had become popular among soldiers in the Roman Empire. Additionally, the popular holiday of Saturnalia ended on December 23, so late December was already a festive time and thus ripe for a new, Christian holiday (much as the proximity of Christmas to Hanukkah prompted the increased modern popularity of that Jewish holiday).

Not all Christians celebrate the birth of Jesus on the same day. For example, some Eastern Orthodox churches date the feast of the Nativity of Jesus according to the Julian calendar, which does not account for certain adjustments that were made when the modern, widely used Gregorian calendar was instituted. Consequently, December 25 on the Julian calendar corresponds to January 7 on the Gregorian calendar. After the Russia-Ukraine War began in 2022, some Eastern Orthodox churches in Ukraine shifted Christmas to the Gregorian December 25 in protest of influence from the Russian Orthodox Church. In Armenia, Christmas is celebrated on January 6, but, among Armenians in Jerusalem and Bethlehem, it is celebrated on the Julian calendar on January 19, which is January 6 on the Gregorian calendar. In the Church of Jesus Christ of Latter-day Saints (LDS), Jesus’ birth is reckoned to have been on April 6, which is also a significant day in the modern church’s history.

BCE, CE, and the missing year 0

Finally, let us attend to the question of why Jesus could not possibly have been born in year 0 and investigate how, in modern chronological thinking, his birth came to be considered the dividing point between two historical eras.

The calendar system widely used around the world today, which divides between bce and ce, developed gradually over the course of the first centuries after the time of Jesus. In the 5th century ce a system based on the Great Paschal (i.e., Passover), or Dionysian, period was devised to establish the date of Easter. That system combined a solar cycle of 28 years in the Julian calendar—when the days of the week and months realign—with the Metonic cycle of 19 years—the time it takes for the full moon to return to the same day of the month. That meant a period of 28 × 19, or 532, years. (The Julian calendar began to be replaced by the Gregorian calendar in 1582, causing the loss of 10 days.)

In the 6th century the Roman theologian, mathematician, and astronomer Dionysius Exiguus claimed that the year now called 532 ce was the first year of a new Great Paschal period and identified the year now designated as 1 bce as the beginning of the previous cycle. He determined that the year now called 1 ce was the year of Jesus’ birth.

Why not 0? Simply put, because zero did not exist as a concept in Europe until the 13th century, when it was introduced there by the Italian mathematician Fibonacci. The most widely used chronology still goes from 1 bce to 1 ce, and this is why new decades and centuries begin with years ending in 1.

Dionysius of Exiguus also devised the system of anno Domini (“in the year of our Lord”). The idea was further popularized in the 8th century by the Anglo-Saxon theologian, historian, and chronologist St. Bede the Venerable, who wrote the system’s name in full as anno ab incarnatione Domini (“in the year from the Incarnation of our Lord”). Bede also mentioned the era that became known as “before Christ,” or, as he put it, anno igitur ante incarnationem Dominicam (“so in the year before the Incarnation of the Lord”). That notion was later expanded into other variants, such as ante nativitatem Christi (“before the birth of Christ”).

The bc-ad system has gradually been replaced with the more secular—but still chronologically equivalent—terms bce and ce, referring to the so-called Common Era, first sporadically in the 18th century and more consistently in the late 20th and early 21st centuries.