Inter gravissimas

"Inter gravissimas" was a papal bull issued by Pope Gregory XIII on February 24, 1582. The document reformed the Julian calendar and created a new calendar which came to be called the Gregorian calendar, which is used in most countries today.

Description

The intention of this bull was "to restore" the previous calendar so that "the calendar itself will never need published any further change".

By "restore" Gregory meant to move the vernal equinox close to March 21 (removing ten days of drift) and the Paschal Full Moon to the 14th day of the moon (removing three days of drift), near where they had been during the Council of Nicaea (May 20 - August 25, 325), even though that council did not specify any rules. Furthermore, the Roman Catholic Church did not even use these rules until Dionysius Exiguus translated the rules of the Church of Alexandria from Greek into Latin in 525. Britain adopted them at the Council of Whitby in 664 and France adopted them about 775. Before these years, France and Rome used the tables of Victorius of Aquitaine, which were published in 457. Britain before 664 and Rome before 457 used an 84-year Paschal cycle called the Latercus.

Gregory also sought to make changes to the calendar to ensure that, in the future, the equinox and the 14th day of the Paschal moon, and consequently Easter Sunday, did not move from their positions.

The changes made to the Julian calendar were as follows:

1. reduction of the number of leap years - centennial years, such as 1700, 1800, and 1900 ceased to be leap years, but years that can be divided by 400, such as 1600 and 2000 continued to be;

2. turning back extra days - October 4, 1582 was to be followed by October 15, 1582 and these 10 missing days were not to be counted in calculating end days of loans, etc.;

3. consequently, Easter will be computed via new Paschal tables.

The name of the bull consists of the first two words of the bull, which starts: "Inter gravissimas pastoralis officii nostri curas…" ("Among the most serious duties of our pastoral office…").

Attached to the bull were six canons which enabled the computation of the new Gregorian Easter and two calendars listing saints' days, one for the last 2½ months of 1582 and another for the entire new Gregorian year.

The bull, canons, and calendars were reprinted as part of the front matter of the principal book explaining and defending the Gregorian calendar, Christoph Clavius, "Romani calendarij à Gregorio XIII. P. M. restituti explicatio" (1603), which is tome V in his collected works "Opera Mathematica" (1612).

Adoption

Though Gregory's reform was "enacted" in the most solemn of forms available to the Church, in fact the bull had no authority beyond the Catholic Church and the Papal States. The changes which he was "proposing" were changes to the civil calendar over which he had no authority. The changes required "adoption" by the civil authorities in each country to have legal effect.

For dates on which various countries adopted the Gregorian reforms, see Gregorian calendar.

The Nicene Council of 325 sought to devise rules whereby all Christians would celebrate Easter on the same day. In fact it took a very long time before Christians achieved that objective (see Easter for the issues which arose). However, the bull "Inter gravissimas", which was not immediately adopted by many European countries, became the law of the Catholic Church. It was not recognised, however, by Protestant Churches nor by Orthodox Churches and others. Consequently, the day on which Easter was celebrated by different Christian Churches again diverged.

External links

* [http://www.bluewaterarts.com/calendar/NewInterGravissimas.htm Inter Gravissimas] la icon fr icon en icon
* en icon la icon fr icon
* [http://henk-reints.nl/cal/audette/calgreg.html Les textes constitutifs du calendrier grégorien] (bull, canons, and calendars) la icon fr icon
* [http://mathematics.library.nd.edu/clavius/ Opera Mathematica of Christoph Clavius] (vol. V contains his works on the Gregorian calendar)

References