Europe's Calendar
Despite territorial, political and linguistic differences, Europe uses the same calendar. Wherever you are in the continent, the rest is either just entering, just leaving, or in the middle of, the same date. This dating system, used by Europe and the rest of the 'westernized' world, was introduced in 1582; it is the Gregorian Calendar. However, this uniformity is a modern luxury, and for most of the early modern and modern period Europe operated under several calendars which were weeks, and in the case of Ottoman territories years, apart. This is an account of the introduction, and adoption, of the Gregorian Calendar.
Problems with the Julian Calendar
Until 1582 Europe operated in the Julian Calendar, a system of dating which used a year of 365 days, with a 366th every four years. Unfortunately, the Julian calendar had a minor error: the average Julian year was 365 days and 6 hours (the extra quarter being added in the leap years), while the actual solar year is 365 days, 5 hours, 48 minutes and 46 seconds, a difference of just over eleven minutes. (Please note: there is some debate among astronomers and other parties as to what actually constitutes the solar year, and these figures can vary by several seconds.) As a result, for every Julian year that passed the human calendar became increasingly out of synch with the natural solar cycle.Considered alongside a human lifespan, eleven minutes a year is almost irrelevant as it takes over a 130 years to gain a whole day. However, by 1582 the Julian calendar had been in use for well over a millennia and a half, and Europe had become 12 days removed from the natural cycle. Seasons appeared earlier in the year, and the informal agricultural calendar - the time for ploughing, sowing and harvesting - was drifting apart from the original traditions.
The Reckoning of Easter
Twelve days may still seem small, especially given the varying onset of our seasons, but it was of great concern for the Catholic Church, whose calendar of festivals was being distorted. The date of Easter was heavily disputed throughout early Christian history, but the Church Council of Nicea attempted to standardize it in 325 AD. Adopting a compromise between the various divisions, Easter was to celebrated on the Sunday after the vernal (spring) Equinox, which in 325 AD was March 21st. However, because of the Julian calendar, the vernal equinox was occurring earlier and earlier in the calendar year, and March 21st was slowly shifting into summer.
Search for an Answer
After a long tradition of concern for Easter's changing season, the process that led to the Gregorian calendar began during the office of Pope Paul III (1534 - 49), when he began to consult with astronomers to find an answer. He also initiated the Council of Trent (1545 - 63) which discussed matters relating to the whole Christian faith. This Council, in conjunction with Pope Pius V (1559 - 65), introduced changes to the lunar calendar and leap year system via a new Breviary and Missal. Consequently, when Pope Gregory XIII was elected in 1572, the problem was still as great as ever, but people were suggesting solutions already grounded in years of thought. Gregory established a commission to investigate, which was led by Christopher Clavius, one of the astronomers approached by Pope Paul III over twenty years earlier.
The Gregorian Calendar
Clavius built on the work of another astronomer, Luigi Lilio, and in 1582 Gregory issued a Papal Bull entitled Inter Gravissimas. This introduced the 'Calendar', which incorporated reforms to the old Julian system and made an immediate change to the existing date. Known as the 'New Style' (with the Julian referred to as the 'Old Style'), this calendar would later take the Pope's name - hence 'Gregorian'.
The Gregorian Reforms
The reforms were:• Leap years were to occur every four years (a continuation of the existing custom), unless it was a centennial year. These were no longer automatically leap years; instead, centennial years followed the same pattern as normal years: every fourth centennial year was a leap year. (Put simply, Gregory decreed that while 1600 was to remain a leap year, 1700, 1800 and 1900 would not have any extra days, but following these three 2000 would again be a leap year, and so on. These five dates, including our very recent 2000, were explicitly stated in the Inter Gravissimas.) Note: The Julian calendar merely had a leap year every four years. It was sheer coincidence that, once the Roman numerals were changed into numbers, the years were, and remained, divisible by four.
• The extra leap day was moved from within February itself to February 29th.
• 10 days were dropped from the existing date: October 4th 1582 was followed by October 15, 1582.
• The rules for the positioning of Easter were changed.
• Contrary to many reports, the Bull made no mention of, or change to, the date of New Years day.
