Whats the difference between the Gregorian and the earlier Julian calendar system?
The average length of a year in the Julian Calendar is 365.25 days (plus one additional day being added every four years). This is significantly longer than the “real” length of the solar year, 365.2422 days. Tthis error accumulates so that after about 131 years the calendar is out of sync with the equinoxes and solstices by one day. Pope Paul III recruited several astronomers, principally the Jesuit Christopher Clavius (1537-1612), to come up with a solution. They built upon calendar reform proposals by the astronomer and physician Luigi Lilio (d. 1576). When Pope Gregory XIII was elected he found various proposals for calendar reform before him, and decided in favor of that of Clavius. On 1582-02-24 he issued a papal bull, Inter Gravissimas, establishing what is now called the Gregorian Calendar reform. The Gregorian reform consisted of the following: -Ten days were omitted from the calendar, and it was decreed that the day following (Thursday) October 4, 1582 (which is October 5, 15
