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WD_404/ 2007
(  Satoshi Kinoshita )
| Series: | Works on paper: Drawings 5 | | Medium: | oilstick on paper | | Size (inches): | 31.1 x 21.4 | | Size (mm): | 790 x 544 | | Catalog #: | WD_0404 | | Description: | Signed, date and copyright in pencil on the reverse.
Gregorian calendar -
The Gregorian calendar is the calendar in current use in the Western world, both as the civil and Christian ecclesiastical calendar. Instituted by Pope Gregory XIII in 1582, the calendar has 365 days with an extra day every four years (the leap year) except in years divisible by 100 but not divisible by 400. Thus, the calendar year has an average length of 365.2422 days. The Gregorian calendar replaced the Julian calendar, which had become 10 days out of synchrony with the solar cycle. In October, 1582, 10 days were dropped from the calendar. England and the American colonies were late in adopting the calendar. In 1752, they dropped 11 days.
-whatis.techtarget.com/definition/
0,,sid9_gci212214,00.htm
Gregorian calendar -
The Gregorian calendar is the most widely used calendar in the world today. It is a reform of the Julian calendar, first proposed by the Calabrian doctor Aloysius Lilius, and decreed by Pope Gregory XIII, for whom it was named, on 24 February 1582 by papal bull Inter gravissimas.
Years in the reformed calendar continue the numbering system of the Julian calendar, which are numbered from the traditional Incarnation year of Jesus, which has been labeled the "anno Domini" (AD) era,[1] and is sometimes labeled the "common era" (CE), otherwise known as "Christian Era".[2]
The changes made by Gregory also corrected the drift in the civil calendar which arose because the mean Julian calendar year was slightly too long, causing the vernal equinox, and consequently the date on which Easter was being celebrated, to slowly drift forward in relation to the civil calendar and the seasons.
The Gregorian calendar system dealt with these problems by dropping 10 days to bring the calendar back into synchronization with the seasons, and adopting the following leap year rule:
Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100; the centurial years that are exactly divisible by 400 are still leap years. For example, the year 1900 is not a leap year; the year 2000 is a leap year.[3]
In the Julian calendar, all years exactly divisible by 4 were leap years.
Description:
The Gregorian solar calendar is an arithmetical calendar. It counts days as the basic unit of time, grouping them into years of 365 or 366 days. The solar calendar repeats completely every 146,097 days, which fill 400 years, and which also happens to be 20,871 seven-day weeks. Of these 400 years, 303 (the "common years") have 365 days, and 97 - the leap years - have 366 days. This gives an average year length of exactly 365.2425 days - or 365 days, 5 hours, 49 minutes and 12 seconds.
A Gregorian year is divided into twelve months of irregular length (but note that there is a period of 153 days divided over 5 months in an alternating pattern from March to July that repeats from August to December):
No. Name Days:
1 January 31
2 February 28 or 29
3 March 31
4 April 30
5 May 31
6 June 30
7 July 31
8 August 31
9 September 30
10 October 31
11 November 30
12 December 31
A calendar date is fully specified by the year (numbered by some scheme beyond the scope of the calendar itself), the month (identified by name or number), and the day of the month (numbered sequentially starting at 1).
Leap years are all years divisible by 4, with the exception of those divisible by 100, but not by 400. These 366-day years add a 29th day to February, which normally has 28 days. Thus, the essential ongoing differential feature of the Gregorian calendar, as opposed to the Julian calendar, is that the Gregorian omits 3 leap days every 400 years. This difference would have been more noticeable in modern memory were it not for the fact that the year 2000 was a leap year in both the Julian and Gregorian calendar systems.
The intercalary day in a leap year is known as a leap day. Since Roman times 24 February (bissextile) was counted as the leap day, but nowadays 29 February is regarded as the leap day in most countries.
Although the calendar year runs from 1 January to 31 December, sometimes year numbers were based on a different starting point within the calendar. Confusingly, the term "Anno Domini" is not specific on this point, and actually refers to a family of year numbering systems with different starting points for the years. (See the section below for more on this issue.)
Footnotes:
1. ^ This era was created in the 6th century by Roman monk Dionysius Exiguus
2. ^ "Common Era". Merriam Webster Online Dictionary. (2003). Merriam-Webster. Retrieved on 2007-12-13. “Main Entry: Common Era – Function: noun – Date: 1846 – : christian era”
3. ^ Introduction to Calendars. (13 September 2007). United States Naval Observatory.
-en.wikipedia.org/wiki/Gregorian_calendar
The Curious History of the Gregorian Calendar - Eleven days that never were
By Ben Snowden
September 2, 1752, was a great day in the history of sleep.
That Wednesday evening, millions of British subjects in England and the colonies went peacefully to sleep and did not wake up until twelve days later. Behind this feat of narcoleptic prowess was not some revolutionary hypnotic technique or miraculous pharmaceutical discovered in the West Indies. It was, rather, the British Calendar Act of 1751, which declared the day after Wednesday the second to be Thursday the fourteenth.
Prior to that cataleptic September evening, the official British calendar differed from that of continental Europe by eleven days—that is, September 2 in London was September 13 in Paris, Lisbon, and Berlin. The discrepancy had sprung from Britain's continued use of the Julian calendar, which had been the official calendar of Europe since its invention by Julius Caesar (after whom it was named) in 45 B.C.
Caesar's calendar, which consisted of eleven months of 30 or 31 days and a 28-day February (extended to 29 days every fourth year), was actually quite accurate: it erred from the real solar calendar by only 11½ minutes a year. After centuries, though, even a small inaccuracy like this adds up. By the sixteenth century, it had put the Julian calendar behind the solar one by 10 days.
In 1582, Pope Gregory XIII ordered the advancement of the calendar by 10 days and introduced a new corrective device to curb further error: century years such as 1700 or 1800 would no longer be counted as leap years, unless they were (like 1600 or 2000) divisible by 400.
If somewhat inelegant, this system is undeniably effective, and is still in official use in the United States. The Gregorian calendar year differs from the solar year by only 26 seconds—accurate enough for most mortals, since this only adds up to one day's difference every 3,323 years.
Despite the prudence of Pope Gregory's correction, many Protestant countries, including England, ignored the papal bull. Germany and the Netherlands agreed to adopt the Gregorian calendar in 1698; Russia only accepted it after the revolution of 1918, and Greece waited until 1923 to follow suit. And currently many Orthodox churches still follow the Julian calendar, which now lags 13 days behind the Gregorian.
Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals.
Why So Difficult?
Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals. Ancient peoples tied their calendars to whatever recurring natural phenomena they could most easily observe. In areas with pronounced seasons, annual weather changes usually fixed the calendar; in warmer climates such as Southern Europe, Africa, and the Middle East, the moon was used to mark time.
Unfortunately, the cycles of the sun and moon do not synchronize well. A lunar year (consisting of 12 lunar cycles, or lunations, each 29½ days long) is only 354 days, 8 hours long; a solar year lasts about 365¼ days. After three years, a strict lunar calendar would have diverged from the solar calendar by 33 days, or more than one lunation.
The Muslim calendar is hence the only purely lunar calendar in widespread use today. Its months have no permanent connection to the seasons— Muslim religious celebrations, such as Ramadan, may thus occur at any date of the Gregorian calendar.
The phases of the moon have nonetheless remained a popular way to divide the solar year, if only because a 365¼-day year doesn't exactly lend itself to equal subdivision (the 71¼-day month has yet to find favor among menologists). To compensate for the difference in the solar and lunar year, calendar makers introduced the practice of intercalation—the addition of extra days or months to the calendar to make it more accurate. The semilunar Hebrew calendar, consisting of twelve 29- and 30-day months, adds an intercalary month seven times every 19 years (which explains the sometimes confusing drift of Passover—and consequently Easter— through April and March).
Despite its widespread use, the Gregorian calendar has a number of weaknesses. It cannot be divided into equal halves or quarters; the number of days per month is haphazard; and months or even years may begin on any day of the week.
Best of All Possible Calendars?
Despite its widespread use, the Gregorian calendar has a number of weaknesses. It cannot be divided into equal halves or quarters; the number of days per month is haphazard; and months or even years may begin on any day of the week. Holidays pegged to specific dates may also fall on any day of the week, and vanishingly few Americans can predict when Thanksgiving will occur next year.
Since Gregory XIII, many other proposals for calendar reform have been made. In the 1840s, philosopher Auguste Comte suggested that the 365th day of each year be a holiday not assigned a day of the week. The generic "Year Day" would allow January 1 to fall on a Sunday every year. Needless to say, this clever solution was not widely embraced.
The French Revolution also saw an attempt at the introduction of a new calendar. On October 5, 1793, the revolutionary convention decreed that the year (starting on September 22, 1792—the autumnal equinox, and the day after the proclamation of the new republic) would be divided into 12 months of 30 days, named after corresponding seasonal phenomena (e.g. seed, blossom, harvest).
The remaining five days of the year, called sans-culottides, were feast days. In leap years, the extra day, Revolution Day, was to be added to the end of the year. The Revolutionary calendar had no week; each month was divided into three decades, with every tenth day to be a day of rest. This straightforward calendar, however, perished with the Republic.
-www.infoplease.com/spot/gregorian1.html
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