Originally Posted by v8guy
Actually all he did was modify the Julian calendar, put into use by Julius Caesar, hence the name. The Julian calendar didn't have leap years, so by 900 AD or whenever Pope Gregory got involved, the calendar had gotten a few weeks out of whack. So the Pope cancelled a few weeks and instituted the leap-year to keep things correct.
and the julius calendar is based off even older stuff
the egyptians had a close one based on the star sirius, but it would go out of whack, but instead of fixing it, they figured out it would take 1,460 years to correct itself, and they just let it go.