Without the arbitrary decision of a 6th century monk, we would actually be in 2030 and not 2023 and would be preparing to celebrate the transition to 2031 according to the calculations of the German astronomer Johannes Kepler (1571-1630) published in 1614 in De vero anno quo æternus Dei Filius humanam naturam in utero benedictæ Virginis Mariæ assumpsit (which could be translated as “About the true year in which the eternal Son of God took human nature in the womb of the blessed Virgin Mary” ).
Doubting the dates established by his predecessors concerning the year 1, Johannes Kepler focuses on the “star of Bethlehem”, cited in the Bible as the star announcing to the wise men the birth of Jesus, even if a star in the sky cannot indicate a precise location on Earth.
This “star” is according to him a simple alignment of the planets Jupiter and Saturn, which creates a luminous point in the night and which the trained eye can spot. He determines according to the trajectory of the planets that this alignment could only have taken place seven years before Jesus Christ himself, around April 12, October 3 or December 4 of the year – 7.
Kepler’s calculations would much later be confirmed by Pope Benedict XVI, who in 2012 mentioned a date “to be fixed a few years before” of approximately “six or seven years” in The Childhood of Jesus. Less categorical than the German astronomer, he estimates that it could well be “four years” according to “Chinese chronological tables”.
An arbitrary date dating back to the 6th century
So where does the convention that resulted in determining astronomers’ “year zero” come from? It all dates back to the 6th century and the work of a Roman monk, Dionysius the Little, recalled Libération for the festivities of the year 2000. At the request of Pope John I, the ecclesiastic, who is also a mathematician and astronomer, “s ‘commits to a complete overhaul of the division of time based on the Christian faith’. This reform will be approved by Pope John II in 533.
Goodbye to the floating date of the birth of Christ, which for two centuries was celebrated on April 19, March 28 or even January 6; the monk decides to start the Christian year on December 25, the date of Christ’s birth according to him, and no longer at Easter, which commemorates the resurrection of Jesus.
The 6th century not knowing the use of zero, Dionysius the Little began his Christian era in the year 1. But above all, errors in calculations and historical reconstruction led to the year of Jesus’ birth being shifted: according to historians, the latter would have been born during the reign of Herod, who died in… – 4 BC
