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Astro*Dictionary by Michael Erlewine





4 articles for "Gregorian Calendar"

Gregorian Calendar [Astro*Index]

Instituted in AD1582 by Pope Gregory XIII, primarily as a basis for regulating Easter and the ecclesiastical calendar. A solar calendar, it is distinguished by the system of intercalation adopted for keeping the calendar year in adjustment with the tropical year, and was constructed by modifying the Julian calendar. The mean Julian calendar year of 365.25 days exceeds the length of the tropical year by about 11m14s. The continual accumulation of this excess amounts to about 3 days every 400 years, and causes a gradual progressive change in the calendar dates of the seasons. This defect in the Julian calendar had produced a very noticeable effect on the date of Easter. As Easter was the Christian continuation of the Jewish Passover, the date was fixed by rules that were intended to keep it near the Vernal Equinox, because the Passover was overved on 14 Nisan, and in the ancient Jewish calendar, the beginning of this month was determined by observation of the lunar crescent nearest the Vernal Equinox. In practice, the date of Easter was determined from tables in which the lunar months were based on the Metonic cycle and MAR 21 was adopted as a fixed date for the equinox. Consequently, as the actual vernal equinox gradually occurred earlier in the calendar, the date of Easter became progressively later relative to the seasons; by the 16th century, the equinox had fallen back to about MAR 11, and Easter was tending nearer and nearer toward the summer.

The Gregorian reform of the Julian calendar consisted of the following changes:

(1) Omitting 10 days from the calendar reckoning, the day next after AD1582 OCT 04 being designated AD1582 OCT 15, for the purpose of restoring the date of the actual Vernal Equinox to MAR 21;

(2) Adopting a different rule for leap year, by omitting the intercalary day in centurial years that are not divisible by 400, such as 1700, 1800, 1900, and 2100, in order to correct the error of the Julian calendar (where an intercalary day is inserted every 4 years);

(3) Fixing rules for determining the date of Easter in the revised calendar. The week was not modified in any way; special provision was made that the sequence of the days of the week was not broken.

The mean length of the Gregorian calendar year is 365.2425 days. At the completion of a 400-year calendar cycle, the cumulative discrepancy with the tropical year is only a few hours. The Gregorian calendar was at once officially adopted for civil and religious purposes in Roman Catholic countries. During the following centuries, it came into almost universal use throughout the West, although with some diversity between civil and ecclesiastical practice; and it is widely used for some civil purposes in countries which have official native calendars. The dates of the official adoption of the Gregorian calendar differed from country to country. In some regions, this calendar came into use gradually without official action. The introduction by legal action was in many cases not completely accepted among the people for a long period, and quite often did not affect ecclesiastical customs; for details, especially of the diverse church calendars. In the Gregorian calendar, Easter has not in all cases been fixed strictly according to the Gregorian rules; in particular, it has occasionally been determined astronomically, e.g., by the German Protestants from 1700-1776, in Sweden from 1740-1844, and by the Eastern Orthodox Churches since 1923. At a meeting of a Congress of the Orthodox Oriental Churches held in Constantinople in 1923 MAY, the Julian calendar was replaced by a modified Gregorian calendar in which century years are leap years only when division of the century number by 9 leaves a remainder of either 2 or 6, and Easter is determined by the astronomical Moon for the meridian of Jerusalem. The change was such that 1923 OCT 01 (Julian) became 1923 OCT 14 in the new calendar.

See also:
♦ Solar ♦ Tropical Year ♦ Julian Calendar ♦ Hebrew Calendar ♦ Vernal Equinox ♦ Lunar Crescent ♦ Metonic Cycle ♦ Leap Year
Gregorian Calendar [Munkasey M.]

The calendar type in popular usage now in the United States.

See also:
♦ Solar ♦ Tropical Year ♦ Julian Calendar ♦ Hebrew Calendar ♦ Vernal Equinox ♦ Lunar Crescent ♦ Metonic Cycle ♦ Leap Year
Gregorian Calendar [DeVore]

v. Calendar.

See also:
♦ Calendar
Gregorian Calendar, Adoption of [Astro*Index]

Although the Gregorian calendar was at once officially adopted for civil and religious purposes in Roman Catholic countries, so that the day next after AD1582 OCT 04 became AD1582 OCT 15, official adoption in other countries did not immediately follow.

The following list gives the dates of official adoption of the Gregorian calendar, in the form of double dates that give the corresponding Julian/Gregorian dates for the first day on which the Gregorian calendar was used.

Alaska:1867 OCT 18.
Albania:1912 DEC, for civil purposes.
Belgium:(Sources disagree) 1582 DEC 22/1583 JAN 01 in Flanders, Brabant, Hainaut, and other souther provinces;
1582 DEC 15/25 in Flanders, Hainaut, Luxembourg, and other souther provinces;
1583 in Flanders.
Bulgaria:(Sources disagree) 1915;
1916 APR 01, for civil purposes.
Chinese Republic: (Sources disagree) 1912 JAN 01, by Sun Yat Sen;
1912, but 1912-1928, both Gregorian date and the Chinese calendar date were carried on official documents;
1929 JAN 01.
Denmark:1700 FEB 19/MAR 01.
Egypt:1875, by ordinance of Ismail Pasha, for civil purposes.
Estonia:1918 JAN.
Finland: See:Sweden.
France:1582 DEC 10/20 in France and Lorraine, by edict of Henry III.
Brixen    1583 OCT 06/16
Carinthia 1583 DEC 15/25
Salzburg  1583 OCT 06/16
Styria    1583 DEC 15/25
Tyrol     1583 OCT 06/16
Bohemia   1584 JAN 07/17
Moravia   1584 JAN 07/17
Alsace                 1648 (after Peace of Munster)
Strassburg (city)      1682 FEB 06/16
Strassburg (bishopric) 1583 NOV 12/22, or
                       1583 NOV 17/27
Aachen                  1583 NOV 04/14
Augsburg                1583 FEB 14/24
Augsburg (bishopric)    1583 FEB 14/24
Baden (marquisate of)   1583 NOV 17/27
Bavaria                 1583 OCT 06/16
Bavarian bishoprics     1583 OCT 06/16
Cologne (city)          1583 NOV 04/14
Eichstadt               1583 OCT 06/16
Freising                1583 OCT 06/16
Hildensheim (bishopric) 1631 MAR 16/26
Julich                  1583 NOV 03/13
Lausitz                 1584 JAN 07/17
Mainz (archbishopric)   1583 NOV 12/22
Munster (city & county) 1583 NOV 17/27
Neuburg Palatinate      1615 DEC 14/24
Osnabruck (city)        1624
Paderborn (bishopric)   1585 JUN 17/27
Prussia (ducky)         1610 AUG 23/SEP 02
Regensburg              1583 OCT 06/16
Silesia                 1584 JAN 13/23
Trier (archbishopric)   1583 OCT 05/15
Westphalia (dauchy)     1584 JUL 02/12
Wurzburg (bishopric)    1583 NOV 05/15
Kaiser and Parliament   1584 JAN 07/17
Protestant Germany      1700 FEB 19/MAR 01

Under Frederick the Great, Gregorian reckoning was
adopted in 1775 under the name of "improved calendar."
Basel, Bern, and Biel    1701 JAN 01/12
Fribourg                 1584 JAN 12/22
Geneva                   1701 JAN 01/12
Lucerne                  1584 JAN 12/22
Mulhausen                1701 JAN 01/12
Neuchatel                1701 JAN 01/12
Prattigau (10 districts) 1812
Sargans                  1701 JAN 01/12
Schaffhausen             1701 JAN 01/12
Schwyz                   1584 JAN 12/22
Solothurn                1584 JAN 12/22
Thurgau                  1701 JAN 01/12
Uri                      1584 JAN 12/22
Zug                      1584 JAN 12/22
Zurich                   1701 JAN 01/22
Federal congress         1583 NOV 10

Appenzell (Protestant half); separated from the Roman
Catholic half in 1597, and remained on Julian calendar.
Graubunden: Gregorian calendar adopted at first only by Roman Catholic districts in upper Rhine valley. The others retained Julian calendar until into 18th century.
Valais: 1622, except Sitten, Siders, Leuk, Raron, Visp, Brieg, and Gorns, which changed in 1656.
Great Britain and Dominions: 1752 SEP 03/14, by Act of Parliament, passed 1751 MAR 18; at the same time, the beginning of the year was changed from MAR 25 to JAN 01, commencing with the year 1752.
Hungary: 1587 OCT 22/NOV 01.
Italy: 1582 OCT 05/15.
Japan: 1873 JAN 01.
Jugoslavia: 1919, according to Fotheringham.
Latvia: Gradual use for civil purposes during the German occupation 1915-1918.
Lithuania: 1915, by teh Catholic Church, which represent three-quarters of the population.
Luxembourg: 1582 DEC 15/25.
Netherlands: 1582-1583 in Catholic States; 1700-1701 in Protestant States; but different sources disagree on the exact dates.
Poland: 1582 OCT 05/15. In the Russian part of Poland, the Gregorian calendar was introduced by teh German occupation troops 1915 MAR 21.
Portugal: 1582 OCT 05/15.
Roumania: 1919 APR 01/14.
Spain: 1582 OCT 05/15.
Sweden: 1753 FEB 18/MAR 01. Finland was then a part of Sweden.
Turkey: 1727 JAN 01.
USSR: 1918 FEB 01/14 for civil purposes.


See also:
♦ Year


Astro*Index Copyright © 1997 Michael Erlewine


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