The work of a sixth-century monk helped
lay the groundwork for establishing
December 25 as the birthdate of Jesus.
Dionysius Exiguus was born about 470 A.D.
in Scythia(modern-day Romania).
He moved to Rome where he was part
of the Roman Curia, translating Church canons
from Greek into Latin.
Dionysius became known as the most learned
abbot of Rome.
Dionysius is said to have developed the concept
of the Christian Era or Anno Domini (A.D.),
which would impact both the Julian and Gregorian calendars.
In 525 A.D., Dionysius began figuring out
future dates for the celebration of Easter.
Based on those calculations, he also determined
that Jesus was born December 25 but
he mistakenly placed the date
in what turned out to be 1 A.D.

from "The Little Blue Book",
Advent and Christmas Seasons 2010-2011
based upon the writings of Bishop Ken Untener
(1937-2004).