It’s obvious that Jesus was born on December 25, A.D. 1., right? Not so fast. What we do know is that Herod the Great (who killed all the babies in Bethlehem younger than two years of age) died in the Spring of 4 B.C., according to the Jewish historian Josephus1. The king was quite alive during the visit of the Wise Men in the Nativity story told in the Gospel of Matthew. So Jesus would have to have been born before this time, anywhere from 7 B.C to 4 B.C. (Before Christ, or before himself!)

Calendar Gap

Why is there a gap of this much time in our modern calendar? We owe this to a Roman monk-mathematician-astronomer named Dionysius Exiguus, or Dennis the Little, but known to his close friends as Dennis the Humble. During the 6th century A.D., he unwittingly committed what has become history’s most significant numerical error as it relates to the calendar. As he tried to reform the Western calendar to center around Jesus’ birth, he erroneously placed the date of the Nativity in the year 753 “from the founding of Rome” (753 a.u.c. or Ab Urbe Condita), even though Herod died only 749 years after the founding of the city of Rome, as everyone knows; it was in all the papers. The cumulative effect of Dionysis’ calendar error, which is the same calendar we use today, was to give the correct traditional date for the founding of Rome. Ultimately, however, the calendar is at least 4 to 7 years off for the birth of Christ.

    Did you celebrate the Y2K change of Millennium in 1997?


Some recent research suggests that the dating of Herod’s death might be up for debate and could be dated 1 B.C. The argument is that either the counting of his reign was off, or that there is a typesetting error in all editions of Josephus since 1544. I tried to get to the bottom of this by researching an earlier edition of Josephus at the British Library in London, but could only get my hands on a French translation from 1492. Regrettably, I couldn’t read medieval French.

Bill Petro, your friendly neighborhood historian

If you enjoyed this article, please consider leaving a comment or subscribing to the news feed to have future articles delivered to your feed reader or your email.

About billpetro

Bill Petro is a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.


  1. aruna on October 18, 2011 at 7:34 am

    again, very interesting and humorus, thanks to the friendly neighborhood historian.


  2. JohnH on December 11, 2012 at 4:18 pm

    A great article by a PhD astronomer on dating Christ’s birth, placing it in 2BC — you might enjoy this.

  3. mao mathew on March 20, 2016 at 8:08 am

    its been a blessing God bless you Bill Petro

  4. mao mathew on March 20, 2016 at 8:08 am

    its been a blessing God bless you Bill Petro sir

  5. Mark Boehm on November 30, 2018 at 11:28 am

    Ok, so call me ignorant but what i dont understand is, they sat jesus was born between 4 and 6 B.C. but how can that be when B.C. stands for before Christ. So he was born 4 yrs b4 was born?

    • billpetro on November 30, 2018 at 11:43 am


      You got it! Crazy isn’t it? The concept of “Before Christ” and “in the year of our Lord” — Anno Domini, or AD — was developed long before the medieval calendar reform of Dennis the Little. He had started with the old Julian Calendar and placed the birth of Christ in 753 after the founding of the city of Rome, which was the previous anchor point for the ancient calendars. Add Josephus’ reckoning of the date of the death of Herod the Great, and you get the situation we have today.


Leave a Reply