In the book Jesus of Nazareth: The Infancy Narratives published on Wednesday, the octogenarian pontiff claims the mistake was made by a sixth century monk known as Dionysius Exiguus.
The calculation of the beginning of our calendar - based on the birth of Jesus - was made by Dionysius Exiguus, who made a mistake in his calculations by several years, the book reads.
The actual date of Jesus birth was several years before, it asserts.
Many had challenged the authenticity of the Christian calendar with many historians putting Christs date of birth sometime between 7 BC and 2 BC.
The point about Christs date of birth is not the only controversy raised in the Popes new book.
He also said that contrary to the traditional nativity scene, there were no oxen, donkeys or other animals at Jesus birth.
He also rejects arguments offered by some scholars that the prophet was born in Nazareth, but rather insists he was born in Bethlehem.
Christian academics agree with the Pope that the Christian calendar was wrong, that Jesus was born several years earlier than commonly thought, and that the idea that Christ was born on Dec. 25 also has no basis in historical fact.
But striking is the highly sensitive issues, which cast doubt over the keystones of Christian tradition are now raised by the leader of the worlds nearly one billion Catholics.