Gregorian Calendar Year. Gregorian calendar, solar dating system now in general use. The gregorian calendar was instituted by pope gregory xiii in 1582 and quickly adopted by much of catholic, but not protestant, europe.

Invented in 1582, the system adopted a leap year cycle different than the one employed by the julian calendar. The gregorian calendar was instituted by pope gregory xiii in 1582 and quickly adopted by much of catholic, but not protestant, europe.