Who Started The Gregorian Calendar. The reform, which established what became known as the gregorian calendar and laid down rules for calculating the date of easter, was well received by such astronomers as. It was introduced by pope gregory xiii as a way of correcting the julian calendar and its yearly measurements.

The gregorian calendar was introduced in 1582 by pope gregory xiii to reform the previous julian calendar, which had become misaligned with the seasons. In 1582, pope gregory xiii reformatted the julian calendar.