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Dating Jesus’ Life: Past and Present Perspectives

It is difficult to overlook the ever-widening gap between this quasi-naturalistic quest for the “real” star of Bethlehem and the approaches taken by modern New Testament scholarship where the infancy stories of Matthew and Luke are treated to often devastating historical criticism.

See Also: Dating the Passion (Brill, 2011)

By C. Philipp E. Nothaft
Department of Hebrew & Jewish Studies
University College, London
July 2012

As the recent flurry of news items concerning alleged new geological and astronomical evidence for the date of Christ’s Passion reminds us, there is an ongoing popular fascination with the idea of using the “hard sciences” to shed light on the events narrated in Scripture.1 Avenues for such an approach seem particularly rich in the case of the life of Jesus, whose birth is said to have been heralded by a star, while his death was accompanied by an eclipse and an earthquake, thus inviting scientists, in particular astronomers, to try their hands at reconstructing the underlying chronology. At the same time, however, it remains a little known fact that some of these techniques and insights have roots that reach back much deeper into Christian tradition than only the last few centuries of biblical criticism. For example, the dating of the crucifixion to 3 April AD 33—presented as a revelation in current news reports—was first proposed not by a modern astronomer, but by the thirteenth-century Franciscan polymath Roger Bacon, who tackled the subject in his Opus majus (ca. 1267), a work solicited by and addressed to Pope Clement IV (1265–1268). Dissatisfied with the many chronological impasses he found in the Bible, Bacon advocated the use of astronomy as the right tool to “reach certainty about the times” (certificare de temporibus)—a method, whose power he subsequently demonstrated by calculating the date of the Passover full moon under which Jesus must have been crucified.

Bacon’s musings on a “scientific” biblical chronology, far-sighted as they were, did not come out of thin air. Already in the third century, early Christian writers such as Hippolytus of Rome (d. 235) had understood that the dates of Jesus’ life were constrained by the celestial cycles of the sun and moon and that some astronomical reckoning devices had to be consulted in order to find out the true date of the crucifixion.2 Up to Bacon’s own time, the instrument of choice for most scholars had been the Easter computus, a 19-year lunisolar cycle based on the Julian calendar, which the medieval Church used to determine the annual dates of its moveable feast days. Due to its inherent astronomical limitations, however, this cycle generally failed to provide an adequate solution to the crucial question of when the Christian Savior was born and died on the cross. In their efforts to nonetheless make the Gospel data agree with the Easter cycle, certain computists of the eleventh and twelfth centuries went so far as to radically shift the dates of Jesus’ life in their relation to history, proposing birth dates in AD 9, 22 BC, or even 33 BC.3

These high medieval revisions were in part reactions against the chronological framework imposed by the Christian or “common” era, still in use today, which had been introduced in the sixth century in Rome by the monk Dionysius Exiguus and gained widespread acceptance in the course of the Middle Ages. Dionysius’ choice of the year AD 1 as the beginning of his count of the “years since the incarnation of our Lord Jesus Christ,” the origins of which are still unexplained, was a significant departure from the view of earlier Church Fathers (e.g., Clement of Alexandria, Tertullian, Orosius, Eusebius of Caesarea, and Epiphanius of Salamis), who had generally converged in dating the nativity two or three years earlier.4 This relative unanimity is explicable by the fact that they all based themselves on the third chapter of Luke’s Gospel, according to which John the Baptist began his activity in the 15th year of the Emperor Tiberius (3:1), while Jesus was “beginning to be about thirty years of age” (3:23) when he received baptism at John’s hands. Tiberius is known to have begun his reign a few weeks after the death of Augustus, in September AD 14, making his 15th year coincide with AD 28/29. Counting back 30 years, early Christian authors arrived at a birth of Jesus in approximately 3/2 BC, which they often designated as the 41st or 42nd year of Augustus.

A return to a nativity in this date-range was urged only in the sixteenth century, after a growing supply of chronological data from ancient Rome and Greece had made it once again possible to correctly determine the reigns of these emperors. The reconstruction efforts of Renaissance chronologers were sometimes supported by astronomical techniques, as when the German mathematician and theologian Paulus Crusius (1525–1572) argued that the lunar eclipse that accompanied Herod’s death (Josephus, Ant. 17.167) could be identified with an eclipse that took place on 9 January 1 BC. Since the Gospel of Matthew indicated that Herod was still alive when Jesus was born, this shifted the date of his nativity back to 2 BC.5 The groundwork for modern study of the chronology of Jesus was finally laid at the beginning of the seventeenth century by the astronomer Johannes Kepler (1571–1630), who studied these issues with particular zeal. Struck by the appearance of a “new star” in the night sky between October 1604 and October 1605 (with hindsight identifiable as the second-brightest supernova in recorded history), Kepler hypothesized that the star mentioned in the nativity account of Matthew’s Gospel must have been a similar event, which he thought was precipitated by a rare and astrologically significant triple-conjunction of Jupiter and Saturn that took place in 7 BC. Based on this conjunction, he decided to shift the birth of Jesus to late 6 BC/early 5 BC—a move he partly justified by tying the demise of Herod to an earlier eclipse than Crusius had envisaged, arriving at a (historically correct) death date in 4 BC, two years after the Magi had first seen the star (Mt 2:16).6

Kepler’s astronomical-astrological approach to the “star of Bethlehem” has had an astonishingly long afterlife. To this day, hardly a Christmas season goes by without the appearance of “new scientific” explanations of the phenomenon, which have thus far ranged from various types of planetary conjunctions to comets, meteor showers, and even a U.F.O.7 While Kepler identified the “star” itself as a nova-type phenomenon, nineteenth- and twentieth-century theorists have more often preferred to link it straight away with the aforementioned planetary conjunction of 7 BC. The latter’s attraction lies not only in the fact that it allows for a precisely calculable date, but also in that it enables one to locate the journey of the Magi in a historical context of prophecy and astrological divination, in which a conjunction of Jupiter (= ruler) and Saturn (= the Jewish people) in Pisces (= Palestine) could be read as signaling a new king of the Jews.8

At the same time, however, it is difficult to overlook the ever-widening gap between this quasi-naturalistic quest for the “real” star of Bethlehem and the approaches taken by modern New Testament scholarship where the infancy stories of Matthew and Luke are treated to often devastating historical criticism.9 Understandably perhaps, astronomers with a bent for solving biblical puzzles in their free time have rarely paid attention to the kind of caveats that were already raised in 1917 by the historian of astrology Franz Boll, to whom the original wording of Matthew’s Greek pointed, if anything, to a certain familiarity with the ancient folk-belief that the birth of each man is accompanied by the apparition of a new star (Pliny, Natural History 2.28).10 Others, including the pioneering historian of religion Hermann Usener, had previously gone even further and pointed to a whole range of ancient sources that show how the motif of celestial portents was firmly rooted in the ancient imaginaire surrounding the birth of regal and messianic characters.11 In the light of these and many more recent evaluations of the story, which have variously relegated Matthew’s star to the realm of myth or midrash, it seems worth asking if the common practice of assigning the birth of Jesus to a date between 7 and 4 BC, as is currently still done in countless textbooks and encyclopedias, should be continued. The upper limit of 7 BC, as we have seen, is clearly influenced by Kepler’s no longer tenable hypothesis of the planetary conjunction, while the terminus ad quem of 4 BC is predicated on the assumption that Jesus was still born during the reign of Herod the Great, as both Matthew (2:1) and Luke (1:5) indicate. But how trustworthy are both Gospel accounts with regard to this chronological relation between Jesus and Herod?

With regard to Matthew, the prospect certainly appears rather dim. Once the legendary nature of the infancy story in Matthew 2 has been recognized, there is little reason to further uphold the notion that the presence of Herod in this story has any bearing on the historical circumstances of Jesus’ birth. Its inclusion can be easily explained by the author’s wish to offset the birth of the Messiah with a powerful antagonist, construed after the model of the Pharaoh in the book of Exodus, who schemes to kill Israel’s newborn sons, but cannot prevent the birth of Moses. The numerous striking parallels that exist between later rabbinic embellishments of this story, as already attested by Flavius Josephus (Ant. 2.205–9), and the Matthean nativity account have not escaped the attention of scholars. Indeed, the Assumption of Moses, written at the beginning of the first century, already contains a vaticinium ex eventu that commemorates Herod as the king who “will slay the old and the young, and shall not spare. … And he will execute judgments on them as the Egyptians executed upon them.”12

Since Jesus was probably known to have been crucified in the early 30s of the common era, it was not difficult to make Jesus and Herod into contemporaries, regardless of whether this claim rested on fact or not. The same observation holds true for Luke’s infancy story, which implies that John the Baptist was conceived during Herod’s reign, but whose reliability is put into question by his account of the census which was supposedly conducted when Quirinius was governor of Syria (2:1–5). From extra-biblical sources, it is known that this census took place in AD 6/7 and the numerous attempts to reconcile the passage with traditional assumptions about the birth year of Jesus have done little but to further erode the credibility of the Lucan author in this respect.13 Since claims about Jesus’ adult years as a preacher in Galilee and Judea are certainly more trustworthy than those about his infancy, it seems that we are left with Luke 3 as the only feasible indication of Jesus’ birth year. Any use of the information contained therein is made difficult by the vague phrasing in 3:23, according to which Jesus “began to be about thirty years of age” (ὡσεὶ ἐτῶν τριάκοντα ἀρχόμενος) at some point in or shortly after the 15th year of Tiberius (3:1), i.e., AD 28/29. Understood as a mere approximation, this is not necessarily inconsistent with a birth in 4 BC; but neither does it completely rule out a birth in 1 BC and AD 1, as Dionysius Exiguus seems to have imagined. Unless one wants to give up talk about the birth year of Jesus altogether, it is perhaps still advisable to take into account the opinions of the ancient Church Fathers, who used Luke 3 to deduce a birth in 3 or 2 BC.


1 See e.g., history/jesus-crucifixion-120524.html. For what the geologists actually said, see Jefferson B. Williams, Markus J. Schwab, and A. Brauer, “An Early First-Century Earthquake in the Dead Sea,” International Geology Review 54 (2012): 1219–28.

2 For a full account, see C. Philipp E. Nothaft, Dating the Passion: The Life of Jesus and the Emergence of Scientific Chronology (200–1600) (Leiden: Brill, 2012).

3 Peter Verbist, Duelling with the Past: Medieval Authors and the Problem of the Christian Era, c. 990–1135 (Turnhout: Brepols, 2010).

4 For these and further examples, see Jack Finegan, Handbook of Biblical Chronology: Principles of Time Reckoning in the Ancient World and Problems of Chronology in the Bible, rev. ed. (Peabody, MA: Hendrickson, 1998), 288–91.

5 Paul Crusius, Liber de epochis seu aeris temporum et imperiorum omnium facultatum studiosis utilissimus (Basel: Henricpetri, 1578).

6 Johannes Kepler, De stella nova, in idem, Gesammelte Werke, ed. Max Caspar et al., 21 vols. (Munich: C. H. Beck, 1937–2009), 1:360–90.

7 See Ruth Freitag, The Star of Bethlehem: A List of References (Washington, DC: Library of Congress, 1979). For a general introduction and overview of such theories, see Finegan, Handbook, 306–20; Raymond E. Brown, The Birth of the Messiah: A Commentary on the Infancy Narratives in the Gospels of Matthew and Luke, 2nd ed. (New York: Doubleday, 1993), 170–73, 610–13; Anthony Aveni, Uncommon Sense: Understanding Nature’s Truths Across Time and Culture (Boulder, CO: University Press of Colorado, 2006), 3–24; David F. Kelley and Eugene F. Milone, Exploring Ancient Skies: A Survey of Ancient and Cultural Astronomy, 2nd ed. (New York: Springer, 2011), 482–85.

8 See, e.g., Roy A. Rosenberg, “The ‘Star of the Messiah’ Reconsidered,” Biblica 53 (1972): 105–9.

9 This point was recently also emphasized by Aaron Michael Adair, “Science, Scholarship, and Bethlehem’s Starry Night,” Sky & Telescope 114 (2007): 26–29.

10 Franz Boll, “Der Stern der Weisen,” Zeitschrift für die neutestamentliche Wissenschaft 18 (1917): 40–48.

11 Hermann Usener, “Die Geburt und Kindheit Christi,” Zeitschrift für die neutestamentliche Wissenschaft 4 (1903): 1–21.

12 The Assumption of Moses (6.4–6), trans. R. H. Charles (London: Adam and Charles, 1897), 22. See further Brown, The Birth, 112–16; Allan Kensky, “Moses and Jesus: The Birth of the Savior,” Judaism 42 (1993): 43–49; Roger David Aus, Matthew 1-2 and the Virginal Conception: In Light of Palestinian and Hellenistic Judaic Traditions on the Birth of Israel’s First Redeemder, Moses (Lanham, MD: University Press of America, 2004); Geza Vermes, The Nativity: History & Legend (New York: Doubleday, 2006), 108–15.

13 Brown, The Birth, 547–56. The contradiction could of course be resolved, if Luke 1:5 were a reference to Herod’s successor Archelaus. See Mark Smith, “Of Jesus and Quirinius,” Catholic Biblical Quarterly 62 (2000): 278–93.