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Календар Календарът (от латински: calendae, наименование на първия ден от всеки месец) е система за организиране на дните с обществена, религиозна или административна цел. Това става чрез именуване на периоди от време, например дни, седмици, месеци, години. Означението на всеки ден в рамките на календара се нарича дата. Датите обикновено се базират на циклите в движението на астрономически обекти, като Слънцето или Луната. Календарът може също така да бъде приспособление (често от хартия), което описва календарната система (например настолен календар). Терминът се използва и в значение на последователност от планирани събития (например културен календар). Съдържание - 1 Календарни системи - 2 Подразделения - 3 Други типове календари - 4 Календарите днес - 5 Списък на календари - 6 Вижте също Календарни системи[редактиране | edit source] Най-често използваните календари са лунни, слънчеви, лунно-слънчеви, планетарни и условни. Лунните календари се ръководят от движението на луната (лунните фази) (например Ислямският календар). Слънчевите календари се базират на субективното възприемане на сезонните промени, пораждани от движението на Слънцето (например Иранският календар). Лунно-слънчевите календари се ръководят от движението на Луната и на Слънцето (например Еврейският календар); Планетарен календар е фиксиран период от време, базиран на броя на видимите небесни обекти (например седмицата); Условните календари не се ръководят нито от Луната, нито от Слънцето (например Юлианският ден, използван от астрономите). Съществуват календари, които се ръководят от движението на Венера (например някои от древните египетски календари). Това е типично основно при цивилизациите в близост до екватора. Слънчеви календари[редактиране | edit source] Дни, използвани от слънчевите календари[редактиране | edit source] При слънчевите календари датата отговаря на слънчевия ден. Денят може да се състои от периода между изгрев и залез слънце, последван от нощта, или може да представлява времето между повтарящи се събития, например два залеза. Дължината може да се променя малко през годината или може да се използва среден слънчев ден. Други типове календари също могат да използват слънчевия ден. Юлиански и Григориански календар[редактиране | edit source] Юлианският календар е въведен от римския диктатор Юлий Цезар през 46 г. пр.н.е. При него месеците са по-дълги от лунния цикъл и затова той не е удобен за следене на лунните фази, за сметка на това много точно показва сезоните. Обикновените години имат 365 дена, а всяка четвърта година е високосна, което означава, че има 366 дни. Така продължителността на средната година е 365,25 дни. За съжаление земната тропическа година (времето, нужно за пълна обиколка на Земята около Слънцето) продължава малко по-малко от 365,25 дни (приблизително 365,242 дни) и така с течение на времето календарът постепенно се разминавал със сезоните. Поради тази причина през 1582 папа Григорий въвежда т. нар. Григориански календар, който през следващите столетия е приет за официален в повечето държави. Бъдещи реформи[редактиране | edit source] От тогава насам са направени многобройни предложения за реформа на календара (например Световен календар и Вечен календар). През 50-те години на 20-ти век в ООН се обсъжда въвеждането на реформиран календар, но тези идеи губят популярността си. Лунни календари[редактиране | edit source] При лунните календари дните се определят от фазата на Луната. Тъй като дължината на лунния месец е приблизително 29,5 дни наброява , изцяло лунните календари бързо се разминават със сезоните. За сметка на това те отразяват точно някои други природни феномени, като например приливите и отливите. Лунно-слънчевите календари се базират на лунни календари, като през няколко години се добавя 13-ти месец и по този начин се постига точност при отразяването на сезоните. Фискални календари[редактиране | edit source] Фискалните календари се използват основно в счетоводните и финансови среди. При тях всеки месец съдържа определен брой седмици и улеснява сравнението по месеци и по години. Пример за такъв календар е календарът 5/4/4, при който януари има 5 седмици, февруари има 4, март има 4 и т.н. Обикновено отчетните календари се нуждаят от 53-та седмица на всяка 5-та или 6-та година, която обикновено се прибавя към декември. Съществува международен стандарт, според който за първа седмица (от понеделник до неделя) винаги се приема седмицата, която съдържа 4 януари според Григорианския календар. Подразделения[редактиране | edit source] Почти всички календари групират последователните дни в „месеци“ и „години“. В слънчевите календари годините продължават приблизително толкова, колкото тропическите години, при лунните месецът отразява лунния цикъл. Тъй като при повечето календари броят на дните в годината не е цяло число, годината не може да се раздели на точен брой месеци и се появяват разминавания, които могат да се коригират с добавянето на допълнителен ден на всеки няколко години. Различните култури използват и други подразделения, като например седмиците, и по този начин се улеснява планирането на събития, които не съвпадат с годините и месеците. Други типове календари[редактиране | edit source] Пълни и непълни календари[редактиране | edit source] Календарите биват пълни и непълни. При пълните календари всички дни са обозначени, при непълните има необозначени дни. Пример за непълен календар е ранният римски календар, според който има 10 месеца (от март до декември), а дните на зимните месеци били обозначавани с общото наименование „зима“. Григорианският календар е пълен. Прагматични, теоретични и смесени календари[редактиране | edit source] Календарите биват разделяни и на прагматични, теоретични и смесени. Прагматичните календари се базират на наблюдения. Такъв календар е Ислямският. Предимството на тези календари е, че те са вечно точни, но при тях трудно се изчислява кога ще се падне дадена дата. Теоретичните календари се базират на строги правила. Такъв календар е Еврейският. При тях лесно се изчислява датата, но за сметка на това те не са точни. Дори да са направени много прецизно, най-късно след няколко хиляди години престават да са такива. След това правилата трябва да бъдат променени, като така той се превръща в смесен календар. Смесените календари са комбинация между прагматичен и теоретичен календар. Обикновено това са теоретични календари, които, след като се открие неточността им, се изменят прагматично. Такава е например замяната на Юлианския с Григорианския календар. И така Григорианският календар се категоризира като пълен, слънчев и смесен. Календарите днес[редактиране | edit source] Най-широко разпространеният календар е Григорианският, използван в почти всички страни. В Израел официалният календар на правителството е Еврейският, но в ежедневието Григорианският календар е по-разпространен. Ислямският календар се използва от всички мюсюлмани за религиозни цели, но в повечето мюсюлмански страни официален е Григорианският. Само в Саудитска Арабия, Кувейт и Йемен ислямският календар е официален. В Иран от 1925 г. се използва иранският календар. Това е слънчев календар, който използва за първа година 622 г. сл. (както при Ислямския). Първите 6 месеца в този календар имат 31 дни, следващите 5 месеца имат 30 дни, а последният има 29 или 30 дни. Съвременният ирански календар използва сложна система за определянето на високосната година, която в повечето случаи се пада на всеки 4 години, но понякога е на 5 години, и така той е много по-точен от Григорианския календар – ако дължината на тропическата година остане постоянна, неточност от 1 ден ще има след повече от 2 милиона години (при Григорианския календар след около 3000 години). Този календар е приет за официален в Афганистан през 1957 г. В България Григорианският календар заменя Юлианския през 1916 г. Списък на календари[редактиране | edit source] - Бахайски календар - Прабългарски календар - Григориански календар - Еврейски календар - Египетски календар - Индийски граждански календар - Ислямски календар - Календар на град Кюстендил - Календар съгласно ISO-8601 - Календар на маите - Китайски календар - Ирански календар - Прабългарски календар - Римски календар - Славянски календар - Фискален календар - Френски революционен календар - Юлиански календар - Японски календар - 19 век
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Calendar A calendar is a system of organizing days for social, religious, commercial or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the sun or the moon. Many civilizations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs. A calendar is also a physical device (often paper). This is the most common usage of the word. Other similar types of calendars can include computerized systems, which can be set to remind the user of upcoming events and appointments. A calendar can also mean a list of planned events, such as a court calendar. The English word calendar is derived from the Latin word kalendae, which was the Latin name of the first day of every month.[1] Contents - 1 Calendar systems - 2 Calendar subdivisions - 3 Other calendar types - 4 Uses - 5 Calendars in use - 6 Physical calendars - 7 Calendar formats - 8 Legal - 9 Online calendars - 10 See also - 11 Sources - 12 Further reading - 13 References - 14 External links Calendar systems[edit] A full calendar system has a different calendar date for every day. Thus the week cycle is by itself not a full calendar system; neither is a system to name the days within a year without a system for identifying the years. The simplest calendar system just counts time periods from a reference date. This applies for the Julian day or Unix Time. Virtually the only possible variation is using a different reference date, in particular one less distant in the past to make the numbers smaller. Computations in these systems are just a matter of addition and subtraction. Other calendars have one (or multiple) larger units of time. Calendars that contain one level of cycles: - week and weekday – this system (without year, the week number keeps on increasing) is not very common - year and ordinal date within the year, e.g. the ISO 8601 ordinal date system Calendars with two levels of cycles: - year, month, and day – most systems, including the Gregorian calendar (and its very similar predecessor, the Julian calendar), the Islamic calendar, the Solar Hijri calendar and the Hebrew calendar - year, week, and weekday – e.g. the ISO week date Cycles can be synchronized with periodic phenomena: - A Lunar calendar is synchronized to the motion of the Moon (lunar phases); an example is the Islamic calendar. - A Solar calendar is based on perceived seasonal changes synchronized to the apparent motion of the Sun; an example is the Persian calendar. - A "luni-solar calendar" is based on a combination of both solar and lunar reckonings; examples are the traditional calendar of China, the Hindu Calendar in India or the Hebrew calendar. - There are some calendars that appear to be synchronized to the motion of Venus, such as some of the ancient Egyptian calendars; synchronization to Venus appears to occur primarily in civilizations near the Equator. - The week cycle is an example of one that is not synchronized to any external phenomenon (although it may have been derived from lunar phases, beginning anew every month). Very commonly a calendar includes more than one type of cycle, or has both cyclic and acyclic elements. Most calendars incorporate more complex cycles. For example, the vast majority of them track years, months, weeks and days. The seven day week is practically universal, though its use varies. It has run uninterrupted for millennia.[2] Solar calendars[edit] Days used by solar calendars[edit] Solar calendars assign a date to each solar day. A day may consist of the period between sunrise and sunset, with a following period of night, or it may be a period between successive events such as two sunsets. The length of the interval between two such successive events may be allowed to vary slightly during the year, or it may be averaged into a mean solar day. Other types of calendar may also use a solar day. Calendar reform[edit] There have been a number of proposals for reform of the calendar, such as the World Calendar, International Fixed Calendar, Holocene calendar, and, recently, the Hanke-Henry Permanent Calendar. Such ideas are mooted from time to time but fail to gain traction because of the loss of continuity, massive upheaval in implementation and religious objections. Lunar calendars[edit] Not all calendars use the solar year as a unit. A lunar calendar is one in which days are numbered within each lunar phase cycle. Because the length of the lunar month is not an even fraction of the length of the tropical year, a purely lunar calendar quickly drifts against the seasons, which don't vary much near the equator. It does, however, stay constant with respect to other phenomena, notably tides. An example is the Islamic calendar. Alexander Marshack, in a controversial reading,[3] believed that marks on a bone baton (c. 25,000 BC) represented a lunar calendar. Other marked bones may also represent lunar calendars. Similarly, Michael Rappenglueck believes that marks on a 15,000-year old cave painting represent a lunar calendar.[4] Lunisolar calendars[edit] A lunisolar calendar is a lunar calendar that compensates by adding an extra month as needed to realign the months with the seasons. An example is the Hebrew calendar which uses a 19-year cycle. Calendar subdivisions[edit] Nearly all calendar systems group consecutive days into "months" and also into "years". In a solar calendar a year approximates Earth's tropical year (that is, the time it takes for a complete cycle of seasons), traditionally used to facilitate the planning of agricultural activities. In a lunar calendar, the month approximates the cycle of the moon phase. Consecutive days may be grouped into other periods such as the week. Because the number of days in the tropical year is not a whole number, a solar calendar must have a different number of days in different years. This may be handled, for example, by adding an extra day in leap years. The same applies to months in a lunar calendar and also the number of months in a year in a lunisolar calendar. This is generally known as intercalation. Even if a calendar is solar, but not lunar, the year cannot be divided entirely into months that never vary in length. Cultures may define other units of time, such as the week, for the purpose of scheduling regular activities that do not easily coincide with months or years. Many cultures use different baselines for their calendars' starting years. For example, the year in Japan is based on the reign of the current emperor: 2006 was Year 18 of the Emperor Akihito. Other calendar types[edit] Arithmetic and astronomical calendars[edit] An astronomical calendar is based on ongoing observation; examples are the religious Islamic calendar and the old religious Jewish calendar in the time of the Second Temple. Such a calendar is also referred to as an observation-based calendar. The advantage of such a calendar is that it is perfectly and perpetually accurate. The disadvantage is that working out when a particular date would occur is difficult. An arithmetic calendar is one that is based on a strict set of rules; an example is the current Jewish calendar. Such a calendar is also referred to as a rule-based calendar. The advantage of such a calendar is the ease of calculating when a particular date occurs. The disadvantage is imperfect accuracy. Furthermore, even if the calendar is very accurate, its accuracy diminishes slowly over time, owing to changes in Earth's rotation. This limits the lifetime of an accurate arithmetic calendar to a few thousand years. After then, the rules would need to be modified from observations made since the invention of the calendar. Complete and incomplete calendars[edit] Calendars may be either complete or incomplete. Complete calendars provide a way of naming each consecutive day, while incomplete calendars do not. The early Roman calendar, which had no way of designating the days of the winter months other than to lump them together as "winter", is an example of an incomplete calendar, while the Gregorian calendar is an example of a complete calendar. Uses[edit] The primary practical use of a calendar is to identify days: to be informed about and/or to agree on a future event and to record an event that has happened. Days may be significant for agricultural, civil, religious or social reasons. For example, a calendar provides a way to determine when to start planting or harvesting, which days are religious or civil holidays, which days mark the beginning and end of business accounting periods, and which days have legal significance, such as the day taxes are due or a contract expires. Also a calendar may, by identifying a day, provide other useful information about the day such as its season. Calendars are also used to help people manage their personal schedules, time and activities, particularly when individuals have numerous work, school, and family commitments. People frequently use multiple systems, and may keep both a business and family calendar to help prevent them from overcommitting their time. Calendars are also used as part of a complete timekeeping system: date and time of day together specify a moment in time. In the modern world, timekeepers can show time, date and weekday. Calendars in use[edit] Gregorian calendar[edit] Calendars in widespread use today include the Gregorian calendar, which is the de facto international standard, and is used almost everywhere in the world for civil purposes. Due to the Gregorian calendar's obvious connotations of Western Christianity, non-Christians and even some Christians sometimes replace the traditional era notations "AD" and "BC" ("Anno Domini" and "Before Christ") with "CE" and "BCE" ("Common Era" and "Before Common Era"). Even where there is a commonly used calendar such as the Gregorian calendar, alternative calendars may also be used, such as a fiscal calendar or the astronomical year numbering system.[5] Islamic calendar[edit] The Islamic calendar, Muslim calendar or Hijri calendar is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in most of the Muslim countries (concurrently with the Gregorian calendar), and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. The first year was the year during which the emigration of Muhammad from Mecca to Medina, known as the Hijra, occurred. Each numbered year is designated either H for Hijra or AH for the Latin anno Hegirae (in the year of the Hijra). Being a purely lunar calendar, it is not synchronized with the seasons. With an annual drift of 11 or 12 days, the seasonal relation is repeated approximately each 33 Islamic years. The Hijri-Shamsi calendar, also adopted by the Ahmadiyya Muslim Community, is based on solar calculations and is similar to the Gregorian calendar in its structure with the exception that the first year starts with Hijra.[6] Hindu calendar[edit] The lunisolar Hindu calendars are some of the most ancient calendars of the world. The names of the twelve months are the same in most parts of India (because they are named in Sanskrit) though the spelling and pronunciation vary slightly and the first month of the year varies from one region to another depending upon past traditions. The standardized Indian national calendar based on the Saka era with 78 CE as the start of the calendar is a lunar Hindu calendar used by the government together with the Gregorian calendar. However, it is not used by the general public which widely uses the Vikrami lunar calendar Vikram Samvat with 56 BCE as the start of the calendar for religious activities and festivals. Vikram Samvat is also the official calendar in Nepal. A lunar month may have 29 or 30 days. In all Hindu calendars the month (from new moon to new or full moon to full) is divided into thirty parts (tithis). The civil date is the tithi in progress at sunrise. As a tithi is shorter than a day, this means that the date sometimes jumps. An additional month is inserted (by repeating a month twice in that year) every few years to synchronize with the solar or sidereal calendar. If the repeated month is, say, Chaitra, the repeated month is named Chaitra-2. At the next correction a month other than Chaitra will be repeated. Others[edit] Eastern Christians of eastern Europe and western Asia used the Julian calendar, that of the old Orthodox church, for a long time in countries like Russia. For over 1500 years, Westerners used the Julian Calendar as well. Virtually all Eastern Christians still make some use of the Julian calendar. While the Gregorian calendar is widely used in Israel's business and day-to-day affairs, the Hebrew calendar, used by Jews worldwide for religious and cultural affairs, also influences civil matters in Israel (such as national holidays) and can be used there for business dealings (such as for the dating of checks). The Chinese, Hebrew, Hindu, and Julian calendars are widely used for religious and/or social purposes. The Iranian (Persian) calendar is used in Iran and some parts of Afghanistan. The Ethiopian calendar or Ethiopic calendar is the principal calendar used in Ethiopia and Eritrea, with the Oromo calendar also in use in some areas. In neighboring Somalia, the Somali calendar co-exists alongside the Gregorian and Islamic calendars. In Thailand, where the Thai solar calendar is used, the months and days have adopted the western standard, although the years are still based on the traditional Buddhist calendar. Bahá'ís worldwide use the Bahá'í calendar. Fiscal calendars[edit] A fiscal calendar generally means the accounting year of a government or a business. It is used for budgeting, keeping accounts and taxation. It is a set of 12 months that may start at any date in a year. The US government's fiscal year starts on 1 October and ends on 30 September. The government of India's fiscal year starts on 1 April and ends on 31 March. Small traditional businesses in India start the fiscal year on Diwali festival and end the day before the next year's Diwali festival. In accounting (and particularly accounting software), a fiscal calendar (such as a 4/4/5 calendar) fixes each month at a specific number of weeks to facilitate comparisons from month to month and year to year. January always has exactly 4 weeks (Sunday through Saturday), February has 4 weeks, March has 5 weeks, etc. Note that this calendar will normally need to add a 53rd week to every 5th or 6th year, which might be added to December or might not be, depending on how the organization uses those dates. There exists an international standard way to do this (the ISO week). The ISO week starts on a Monday, and ends on a Sunday. Week 1 is always the week that contains 4 January in the Gregorian calendar. Physical calendars[edit] A calendar is also a physical device (often paper) (for example, a desktop calendar or a wall calendar). In a paper calendar one or two sheets can show a single day, a week, a month, or a year. If a sheet is for a single day, it easily shows the date and the weekday. If a sheet is for multiple days it shows a conversion table to convert from weekday to date and back. With a special pointing device, or by crossing out past days, it may indicate the current date and weekday. This is the most common usage of the word. In the USA Sunday is considered the first day of the week and so appears on the far left and Saturday the last day of the week appearing on the far right. In Britain the weekend may appear at the end of the week so the first day is Monday and the last day is Sunday. The US calendar display is also used in Britain. Calendar formats[edit] It is common to display the Gregorian calendar in separate monthly grids of seven columns (from Monday to Sunday, or Sunday to Saturday depending on which day is considered to start the week — this varies according to country) and five to six rows (or rarely, four rows when the month of February contains 28 days beginning on the first day of the week), with the day of the month numbered in each cell, beginning with 1. When working with weeks rather than months, a continuous format is sometimes more convenient, where no blank cells are inserted to ensure that the first day of a new month begins on a fresh row. Unlike with geographical maps, where many famous projections are known (such as the Mercator projection), the calendar projection is a matter of such triviality that no names for these exist in common circulation.[citation needed] Legal[edit] For lawyers and judges, the calendar is the docket used by the court to schedule the order of hearings or trials. A paralegal or court officer may keep track of the cases by using docketing software. Online calendars[edit] Web-based calendars have replaced pocket, wall and desk calendars in most business and personal applications.[citation needed] Calendars services like Google Calendar, AOL Calendar etc. provide interactive calendars that can be used in business applications.[citation needed] See also[edit] - List of calendars - Advent calendar - Bulgar calendar - Calendar reform - Calendrical calculation - History of calendars - List of international common standards - List of unofficial observances by date - Real-Time Clock (RTC), which underlies the Calendar software on modern computers. - Time for divisions smaller than one day Calendars in computing[edit] Sources[edit] - Birashk, Ahmad (1993), A comparative Calendar of the Iranian, Muslim Lunar, and Christian Eras for Three Thousand Years, Mazda Publishers, ISBN 0-939214-95-4 - Dershowitz, Nachum; Reingold, Edward M (1997), Calendrical Calculations, Cambridge University Press, ISBN 0-521-56474-3 with Online Calculator - Zerubavel, Eviatar (1985), The Seven Day Circle: The History and Meaning of the Week, University of Chicago Press, ISBN 0-226-98165-7 - Doggett, LE (1992), "Calendars", in Seidelmann, P. Kenneth, Explanatory Supplement to the Astronomical Almanac, University Science Books, ISBN 0-935702-68-7 - Árni Björnsson (1995) [1977], High Days and Holidays in Iceland, Reykjavík: Mál og menning, ISBN 9979-3-0802-8, OCLC 186511596 - Richards, EG (1998), Mapping Time, the calendar and its history, Oxford University Press, ISBN 0-19-850413-6 - Rose, Lynn E (1999), Sun, Moon, and Sothis, Kronos Press, ISBN 0-917994-15-9 - Spier, Arthur (1986), The Comprehensive Hebrew Calendar, Feldheim Publishers, ISBN 0-87306-398-8 - Dieter Schuh (1973), Untersuchungen zur Geschichte der Tibetischen Kalenderrechnung (in German), Wiesbaden: Franz Steiner Verlag, OCLC 1150484 Further reading[edit] - Fraser, Julius Thomas (1987), Time, the Familiar Stranger (illustrated ed.), Amherst: Univ of Massachusetts Press, ISBN 0-87023-576-1, OCLC 15790499 - Whitrow, Gerald James (2003), What is Time?, Oxford: Oxford University Press, ISBN 0-19-860781-4, OCLC 265440481 References[edit] - ^ New Shorter Oxford English Dictionary - ^ Zerubavel, The Seven Day Circle (University of Chicago Press, 1985). - ^ James Elkins, Our beautiful, dry, and distant texts (1998) 63ff. - ^ "Oldest lunar calendar identified". BBC News. - ^ "NASA – Year Dating Conventions". Sunearth.gsfc.nasa.gov. - ^ "Hijri-Shamsi Calendar". Al Islam. External links[edit] - "Calendar". Encyclopedia Americana. - "Calendar". Encyclopædia Britannica (11th ed.). - Calendar FAQ - Invention of calendar in ancient times an educational web site