Calendar

A calendar is a system of location of the dates according to time. Such a system was invented by the men to divide and organize time over long lives. Initially conceived to be in agreement with the astronomical phenomena and cycles it Saisons, the calendars were, in return, also essential to the observation of the astronomical events, Astrologique S but also religious.

The word comes from Latin calendae , “which is called” (verb calare , “to call”). The “Calendes” indicated among Romans the first day of the month which was the beginning of the new moon. (The days were counted with back starting from the “Calendes”, of the “Nones” 5th or 7th day of the month, the “Ides”, 13th or 15th day of the month). This day, the Pontife S announced the date of the movable feasts of the next month and the debtors were to pay their debts entered in the calendaria , “accounts books”.

Units of the calendar

All the historical calendars are based on natural units of duration defined by astronomical phenomena.

The day

In all civilizations, the alternation of the day and night seem to have been the fundamental unit of the location of the flow of the year. This one being due to the rotation of the Earth, the beginning of the day is not simultaneous from one point to another of the terrestrial sphere. Up to one recent time that was not awkward insofar as civilizations lived almost without contact the ones with the others. The development of transport and the possibility of diffusing the hour brought to define, during the 19th century, the concept of Time zone to make correspond one hour given with an apparent position of the sun on the vault of heaven.

The month

The phases of the the Moon being simple to observe, they provided a convenient means of measurement of time. One used lunations to count times higher than a few days. In the areas of the sphere where the seasons are marked little, as in Polynesia, lunation remained a long time after the day the fundamental unit of measurement of time. The Moslem Calendrier modern is also lunar.

As in all the solar calendars, the Mois of the Gregorian Calendrier are not synchronized with the lunar revolution.

The year

Marking the seasons, the revolution of the Earth around the Sun, i.e. the Year, seems to have taken importance with the development of agriculture. This cycle is one relatively long duration and its flow can be located for example by phenomena as the Solstice S. It is thus probable that men used the lengthening of the shades to locate the course of the year, associated with the apparent way of the sun compared to the constellations of the Zodiaque.

The first calendar based over the year seems to have been the Egyptian calendar. According to certain theories, megaliths of the sites of Nabta Playa or Stonehenge, or the shapes of the temples Aztèque S and Maya S could have been used to measure the years.

Combination of the natural units

The astronomical phenomena presented higher being independent, the units which they define are not commensurable: their report/ratio is not an integer.

Vis-a-vis this difficulty, the people chose either to let the calendar desynchronize itself or to empirically readjust it on the celestial phenomena, even if it means to lose the continuity of the days. It is said whereas a calendar is rather arithmetic or rather astronomical.

The year and the day

At our time, a year is worth 365,24220 days. The Egyptian Calendar, then the Calendar Julien and finally the Gregorian Calendrier are an good example of the successive efforts which were made to manage to synchronize the year with the cycle of the Earth around the Sun.

Even our current calendar always presents a light desynchronization of the year, evaluated at a few days (3 days) over 10000 years. It is today illusory to still want to improve the Gregorian adjustment.

The month and the day

The intermediate duration of a lunation is 29 days 12 hours 44 minutes and 2,8 seconds (29,53 days). Thus while making alternate months of thirty and twenty-nine days, and the condition of adding one day every thirty months, one arrives at an acceptable precision. This mechanism was used by all the old lunar calendars to make correspond the day order in the month with the phases of the moon.

The month and the year

A solar year comprises 12,36827 lunations. To establish the calendar year and thus to preserve an agreement between the months and the seasons, the calendars Roman Chaldée NS and added every three years a thirteenth month to their calendar. But the harmonization remained very imperfect.

All the calendars which reached a certain level of precision gave up the idea to synchronize at the same time the lunar month and the solar year and are either purely solar as the Gregorian Calendrier or purely lunar like the Moslem Calendrier. For example in the Gregorian calendar, the months do not follow the phases of the Moon: the year is divisible in exactly twelve months. Those Ci can be grouped by 2 to form one two months, 3 per one quarter and 6 per one six-month period; these two last correspondent with one or two seasons.

One can however quote the exception of the Hebraic Calendrier modern which bases on the Cycle metonic  : 19 years correspond to two hundred and thirty five months. On a nineteen years cycle this calendar thus defines seven thirteen months years and twelve twelve months. It must however be regularly synchronized on the cycle of the Moon because the year and the month thus defined are both slightly surplus.

The season and the year

In most of the calendars, there are 4 Saisons; Spring, be, Fall, Winter. These seasons are not always placed in the same way in the course of the year, if for example the Chinese or the Celts spent the summer from May to July of the Gregorian calendar, the Summer solstice, the day longest being about in its medium, in the European modern calendar, the summer starts with the summer solstice.

In China, the year starts with spring, in Scandinavian countries it started with the festival of the semi-winter (Midtvintersblot), the Winter solstice, became Christmas more recently. That also shows that, in their calendar, the solstices marked the middle of seasons and not the beginnings of the season like today.

Subdivisions of the calendar

The other measuring units of time are only multiples or submultiples of the three natural units described above. Purely arbitrary, they thus strongly varied from one civilization to another.

The hour

The division of the day in precise units is of Egyptian origin and chaldéenne. The first divisérent the day of 24 parts, 12 for the night and 12 for the day. The seconds divided their day into sixty parts as in the calendars vedic of India; starting from the VII E, the Babylonians borrowed from Egypt the division of their day in twelve parts. Many people defined thereafter their concept of hour while cutting out in twelve parts these two periods of variable durations according to the seasons.

The invention of the minute and the second would be also of Babylonian origin, even if it is very improbable that they were able to be located in time with a precision higher than a few tens of minutes.

The contemporary unit of measurement of time is the second which is defined since 1967 by an atomic phenomenon. The time of the every day rests on the universal Time coordinated which is in agreement with the universal Time based on the rotation of the Earth with a margin of less than one second. Our definition of time thus does not rest entirely any more on the astronomical cycles, single fact in the history of Humanity.

Following the deceleration of the Earth by effect of tide, the current Jour is a little longer than that of 1820 which was used for the historical definition of the second. There is thus necessary, punctually, to carry out a jump of second by adding one second additional (even by withdrawing one second, although that never yet occurred) to one or two days of the year to remain synchronized with the rotation of the Earth. These adjustments are irregular because the variations of the period of rotation of the Earth themselves irregular and are still badly explained. These adjustments, announced several months in advance by IERS, take place on preset dates in end of the month, by adding or withdrawing one second at last the one day minute.

The week

The Egyptians, the Chinese and the Greeks grouped the days in decades. The first mention of a Semaine seven days appears among Hebrews who could have borrowed it from Chaldéens. This duration is about that of a phase of the Moon. The adoption of the shabbat as day of rest is due to a biblical command . By generalization, a sabbatical year returns every 7 years. Whereas it is necessary to wait 50 years to find a year jubilaire and its Jubilee.

In Mésopotamie, number 6 was regarded as ostentation, and the number seven like harmful; it was thus recommended anything to undertake the 7,14,21 and 28 of the month. This harmful day was called " sabbatu". It was adopted by the Hebrews.

In Occident, the use of cutting in weeks dates only from the 3rd century of our era. The adoption of the Sunday as day of rest is due to a decree of the emperor Constantin I {{er}} in 321.

In the Gregorian calendar, since one month average comprises approximately 4,34812 weeks, the week is not a subdivision of the month. The same applies to the fortnight (2 weeks). Except obviously for the months of February of nonbissextile years which comprise 4 weeks exactly or two fortnights.

The gloss

The gloss is one 5 years period. With Rome, it represented the space of time separating two censuses.

The century

This word is of Roman origin, but Latin allotted a significance much vaguer to him since according to the authors it could represent from twenty-five to a hundred and sixteen years.

It should be noted that contrary to the usually widespread belief, the last years of the century like 1800, 1900 or 2000 is the last of their Siècle. With definition a calendar starts in the year 1; it is indeed necessary that the year 100 belongs to the 1st century so that it makes hundred years. Thus, the 21e century began on January 1st, 2001.

The era

The era is one period of time which extends since an historical event marking or founder being used as starting point and chosen by convention like year 1 in a Chronologie. They were numerous during the history and are never exclusive.

In a direction more aged and seldom employed, the era also indicates the event founder himself.

The Christian era starts the supposed year of the birth of Jesus-Christ. The Anno Domini, which determines today year 1 at the base of the Gregorian Calendrier, was determined by Dionysius Exiguus (Denys the Small one) in 532.

One can also quote:

  • the era of Rome: the foundation of Rome was used as era by the Romans. Year 1 of our calendar corresponds to year 754 of the era of Rome.
  • the Julienne era: the Calendar Julien between in force in -45, its creation is used like year 1.
  • the Hégire: the calendar Musulman uses the departure of Mahomet for Médine, the July 16th 622 like era.
  • the judaïque era: the October 7th -3761 would correspond according to the Jewish chronologists to the creation of the world. This date is used as era by the Hebraic calendar.
  • the creation of the world (Ass Mundi) -5509 for the calendar of the orthodoxe Church.
  • awakening of the Buddha Gautama (the last historical Buddha) -543 for the Buddhist calendar .
The Mayas of the traditional time (IIIe, 9th century after J. - C.) thought that the divinities more or less regularly remade the men in various matters (wood, corn for example) and that they expected certain behaviors from them to maintain them or not in the existence and abundance or the food shortage. At all events, the Maya scribes estimated to live (and us with them) in a n-ème started creation one day 4 Ahau 8 Cumku of their ritual calendar, the origin day numerically noted 13.0.0.0 .0. in their vigesimal numeration. The specialists generally agree to make correspond the origin of the Maya era to August 13rd, 3114 before J. - C. It seems established that this nth creation should last 13 baktun (i.e. 5200 tun or 5200 “360 days”, or 1.872.000 days years Maya): it should thus finish very soon, in December 2012, and leave room to (n+1) the ème humanity.

Systems of calendars

A calendar is lunar or solar according to whether it privileges the month or the year. In a lunar calendar, the one month intermediate duration must approach that of a lunation: 29,530589 days. In a solar calendar, the duration of the year must be approximately 365,242190 days. During centuries, various calendars were elaborate. One can quote:

Solar calendars

lunar Calendars

lunisolar Calendars

They are lunar calendars which are adjusted at the solar year using intercalated months.

Other calendars

Other

  • the Jour Julien is a process of continuous account of the days related to the Calendrier Julien proleptic

See too

Related articles

External bonds

  • French Calendar French Calendar with every school vacation.
  • Saga Calendars calendars in the world and time.
  • Khalid Chraibi : The problems of the Islamic calendar
  • Calendriers Sexagesimal Lira the date must be as simple as to read the hour.

Be-X-old: Каляндар Fiu-vro: Kallendri Simple: Calendar Zh-min-nan: Le̍k-hoat

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