The unit of measurement that man has historically used to
measure short periods of time is the day, one revolution of
the earth about its axis. For longer periods of time, the year
is used, one revolution of the earth around the sun. The year
is not a whole number of days, but rather 365 and the
fraction 0.2424 days, and that fraction has always been a
problem when the year is put on a calendar. The Egyptian
calendar had a year of 12 months each of 30 days with 5
extra days at the end. That meant that it had about 1⁄4 of a
day error per year, causing the starting date of the year to
slowly drift forward with respect to the seasons about one
full day every 4 years. Cultures in the ancient Near East
developed their own calendars that attempted to address this
error. Some cultures and religions also combined the cycles
of the moon with the sun. In the process of measuring time,
the Egyptians gave us the 24 hours day, the Mesopotamians
gave us minutes and seconds, the ancient Near East gave us
the seven day week (referenced in Genesis) and the Greeks
named the days of the week. The Roman calendar of Julius
Caesar invented an extra day every four years (leap year) to
try and eliminate the factional error. After the Romans,
Christian Europe with the pope as its head adopted that
Julian calendar. By about 700 CE (“Common Era” also
known as “Anno Domini”.- “the year of the Lord” (birth)
abbreviated AD) it had become customary to count years
from the starting point of the birth of Christ (later corrected
by Johannes Kepler to 4 BCE). But the equinox kept
slipping backwards on the calendar one full day every 130
years. If the equinox was wrong, then Easter was celebrated
on the wrong day. Lent and Pentecost are figured from the
date of Easter, so they were also wrong .The situation was
increasingly seen as a scandal. The Julian calendar still had
an 11 minutes and 14 seconds error and by the 16th century
a ten day discrepancy had developed. Pope Gregory XIII
employs a German Jesuit and astronomer, Christopher
Clavius, to find a solution. Clavius suggests an ingenious
adjustment which became the basis of the Gregorian
calendar the one we use today. For century years (or those
ending in ‘00’ ), they should only be leap years if divisible
by 400. This eliminates three leap years in every four
centuries and neatly solves the problem completely. Pope
Gregory immediately adopted the proposal in the papal
states, announcing that the day after October 4 in 1582 will
be October 15 – thus saving the lost ten days. It took some
countries many years to adopt this new Gregorian calendar
and adjust. In 1752 Britain finally adopted and American
inventor Benjamin Franklin welcomed the change, writing,
“It is pleasant for an old man to be able to go to bed on
September 2, and not have to get up until September 14.”
Sources: galileo.rice.edu, infoplease.com
Vatican Corner 12-28-14
