The calculation of time deals with the order and structuring of time or temporal processes. The most common international calendar refers to the Gregorian calendar for the reference dates - era - and is also identical to the order and structure of the Christian calendar with regard to the other aspects .
Aspects of the calculation of time:
- The order of the linear structure of time ("linear calculation of time") - Before Present , million years ago , Lambda CDM model
- The indication of a point in time in the calendar system - time , astronomical chronology
- Agreements and conventions on reference dates of the era - year zero , era
- The calendar order of cyclical structures such as year , month , week , day - calendar calculation
- Agreements and conventions on how the date is written - date format
Calendar and time
For cyclical structuring, the time is usually divided into:
In the context of the clock it is represented in:
The starting point for these recurring time divisions in all cultures was the observation of astronomical phenomena in connection with the sun , the moon and the starry sky . The Gregorian calendar most commonly used worldwide today is a solar calendar .
- The movement of the sun in the sky is shown in the year , day and time . A day is based on the time span between two highs of the sun, while the year is based on the earth's orbit around the sun.
- The month is derived from the movement of the moon , but also, for example, the lunar day Tithi of the Vedic calendar .
- Some long-term periods ( ages ) refer to other astronomical elements in addition to the sun , such as the Platonic year to the precession motion of the earth's axis .
- The Sothic year of the Egyptian calendar refers to the star Sirius .
Annual calculation, various reference points of the annual calculation
The idea of time running linearly arises from the individual sense of time. The division of a human life into years of life results from the memory of the sequence of the solar years . The date of reference of the personal time calculation is the birthday .
A prerequisite for linear time calculations ( annual calculation ) is the agreement of one or more reference dates .
Orientation towards a singularity
The simultaneous creation of space and time can be a singular reference point for time calculations:
- The Lambda CDM model of the universe describes the evolution of the universe since the Big Bang from a singularity in a time calculation with cosmic dimensions. It gives the age of the universe at around 13.8242 billion solar years .
- In Judaism there has been an idea of the unity of time and space and the linear structure of time since ancient times. The space-time continuum ex nihilo arose in the creation of the universe . Jewish researchers set October 6, 3761 BCE as the first day of the Jewish era (see Jewish calendar ). If the seven biblical days of creation are understood as civil sunny days , the biblical word of God on the creation of time and space ( Gen 1.3 EU ) is said to be given on Yom Rishon , October 6th, 3761 BC, 11 p.m., 11 minutes 20 seconds be: "Let there be light , and there was light". Other Jewish researchers pointed out the fact that the sun, as the cause of the sunny day of about 24 hours, was not created until the fourth day of creation. On the first day of creation, with the spreading “Let there be light”, time came into being, which is similar to the Lambda CDM model of the Big Bang. This allowed the opinion that the days of creation can also stand for (different) periods of time , which is reconcilable with the scientific age of the universe , since the Big Bang from a singularity, of around 13.8 billion years.
- The Christian tradition followed the Jewish tradition of creation as the starting point for the calculation of time. However, the results when calculating the “annus creationis mundi” (year of the creation of the world) differed from the number naturalized in Judaism. The first Christian theologian to make creation the reference point for the counting of the year was Gregory the Great . He came to 5184 years until the resurrection of Jesus Christ , which he put on his 33rd year, so that 5151 years remain until the turn of the ages.
Orientation towards the reigns of rulers
In many cultures, the "official calendar" was derived from the assumption of office of the respective ruler. Years are given as “In xx. Year of the reign of ... " ; Examples:
- The Seleucid era began in 312 BC. When Seleukos I Nicator came to power
- In older cultures , lists of kings formed the basis of the calculation of time, for example in Sumer and Egypt .
- The Roman era goes back to consular lists . In them the two acting consuls were noted. They were continued in the imperial era and have been preserved.
- The Diocletian era began in 284 but was not introduced until after Diocletian's death . It was mainly used in the area of the Coptic Church , i.e. in late ancient Egypt , but also in Christian Nubia .
The Indian Era lists many short-lived empires, each with their own chronology starting with a ruler. Many of them have not yet been fixed in chronological order.
- In Hinduism , the Shaka era and the Kaliyuga - age .
- The Gupta Empire begins its calendar with the accession of the first Gupta king Chandragupta I in 319.
- Maues Era: Early first century BC, uncertain
- Azes era: middle of the first century BC, probably identical to the Vikrama era
- Gondophares Era: began at 20
- Saka era: began in 78, perhaps identical to the Kosam / Bandogarh and Lichchhavi era
- Kanishka Era: began between 110 and 130
- Kushan era: began in 227 and was perhaps the continuation of the Kansihka era
- Kushano-Sasanian era: began 233
- Kalchuri Chedi Era: 248
- Ganga Era: 420
Orientation towards religiously significant people
Some cultures and religions based their calendar on their founding figure.
- In Buddhism , the calendar is traditionally based on the day of the death of the Buddha Siddhartha Gautama , who was dated 544 BC by Sinhalese monks. Was established, actually Buddha died around 483 BC. The western year 2000 was the year 2544 in the current Buddhist calendar.
- The Christian communities initially followed the regionally prevailing calendar. The Roman monk Dionysius Exiguus , who died around 545, calculated the year 754 from urbe condita (old Roman calendar) as the year of the birth of Jesus of Nazareth , which then became year 1 in the Christian calendar (1 after the birth of Christ) from the specifications of the New Testament . Beda Venerabilis was the first historian to use this Christian era systematically around 730. It was already in use in Charlemagne's Frankish empire and later spread worldwide from there. Since then, in the Christian world, time has been divided into ante Christum natum , before Christ's birth , and post Christum natum , after Christ's birth. The Christian calendar that is handed down with it, however, is in contrast to the historically probable birth of Jesus of Nazareth in the period from 7 to 4 BC . The abbreviation “AD” ( Latin Anno Domini , in the year of the Lord) is also found in older German-language dates ; by "Lord" is meant here Jesus Christ. In the 20th century, attempts were made to introduce the abbreviation vuZ / nuZ (before or after our era). In English texts, AD (Anno Domini) and BC (before Christ) are widely used.
- The Islamic calendar begins with the year of the Hijra of Muhammad , the breaking of ties and ties between the Prophet and his followers in his hometown Mecca and his move to Medina in AD 622.
- In Bahaitum , the Badi calendar begins on March 21, 1844 in the year of the declaration of Bab .
Orientation towards events
Other times are based on events of religious or cultic significance:
- A year counting common in ancient Greek culture was based on the Olympiads , the first of which was in 776 BC. Took place.
- The Roman year counting from urbe condita is derived from the assumed descent of the Roman people from Aeneas and the legendary foundation of Rome by Romulus . However, it was not systematically used until 400 AD by the Iberian historian Orosius .
Modern time accounting systems
- The French Revolution began in 1792 with the French Revolution Calendar .
- Benito Mussolini introduced the Era Fascista in Italy , which began on October 28, 1922 ( March on Rome ). The year XI of the fascist era began on October 28, 1933.
To simplify the machine calculation with time periods, linear time calculation systems with more or less arbitrarily set zero points were created:
- The Unix time counts the seconds since January 1, 1970, 00:00 UTC .
- The Julian date in its original form counts the days since January 1st −4712 ( 4713 BC ) 12 o'clock GMT
- Modified Julian date : newer variants of the Julian date select November 17, 1858 0:00 GMT, December 30, 1899 ( Microsoft Excel for Microsoft Windows , StarOffice / Apache OpenOffice ) or January 1, 1904 (Microsoft Excel for Macintosh ) as the zero point .
Relative and absolute chronology
In the historical and related sciences there is a distinction between absolute and relative chronology . Here, chronology means a temporal sequence which is considered absolute (for example lists of rulers, dendrochronological sequence) if it can be linked to the present. For example, from precisely dated fixed points, it is known exactly when an element of this sequence existed before our time. Thus the whole sequence can now be dated absolutely. A chronology is referred to as relative if events, finds, etc. can be brought into a chronological sequence with one another, but when determining the age it cannot be determined how long this sequence was before the present, as there is no fixed reference point to the present.
In the European standard EN 28601 (from 1992) the date format (the valid representation of the time calculation) is specified, which is unrestrictedly valid for Germany and Austria (derived from ISO 8601 from 1988). In addition, the current ISO 8601 standard (from 2000) provides for a full scale with a year zero and years with a negative sign . Dating according to Christian tradition regarding before or after Christ without year zero is no longer discussed.
- Hermann Grotefend : Calendar of the German Middle Ages and the modern age. I-II, Hanover 1891-1892 / 98; Reprint Aalen 1970; and: Pocket book of the chronology of the German Middle Ages and modern times. , designed by Hermann Grotefend, 8th edition, obtained from Otto Grotefend , Hanover 1941; anastatic reprints until 1948; 10th ed., Ed. by Th. Ulrich, Hannover 1960; 14th edition 2014.
- Hans Lietzmann : Calendar of the Roman Empire, the Middle Ages and the Modern Age for the years 1-2000 AD. Walter de Gruyter & Co, Berlin 1946.
- Thomas Vogtherr: Time calculation - from the Sumerians to Swatch. Beck, Munich 2006, 3rd edition 2012, ISBN 978-3-406-44763-1 .
- Hermann Reichert : Time Calculation and Time Consciousness . In: Reallexikon der Germanischen Altertumskunde . No. 35 . de Gruyter, Berlin / New York 2007, ISBN 978-3-11-018784-7 , pp. 866-877 .
- Leofranc Holford-Strevens: A short history of the calculation of time and the calendar. Reclam, Stuttgart 2008, ISBN 978-3-15-018483-7 .
- Nikolaus A. Bär : Chronology and Calendar. Retrieved April 7, 2012 (many different conversions and calculations).
- J. Thomann: Conversion of Islamic and Christian dates. Retrieved on April 7, 2012 (English, simple conversion of the two time calculations).
- WikiTimeLine. Retrieved on July 21, 2010 (English, graphic representation of historical events).
- H. Grotefend: Time calculation of the German Middle Ages and the modern age. Retrieved July 21, 2010 .
- Robert Bracey : The Minor Indo-Parthian Eras . Kushan History , accessed July 21, 2010 (English, Indian timescales).
- The Brockhaus multimedia 2009
- Ludwig Basnizki: The Jewish calendar: origin and structure . Jüdischer Verlag, Frankfurt 1998, ISBN 978-3-633-54154-6 , pp. 29-30.
- Arno Borst : Computus. Time and number in the history of Europe . 3rd, revised and expanded edition. Wagenbach, Berlin 2004, ISBN 3-8031-2492-1 , p. 35.
- Robert Bracey : The Minor Indo-Parthian Eras . Kushan History , accessed July 21, 2010 .
- next to BCE / CE - Google Book Statistics Ngram Viewer
- Hermann [and from the 8th edition Otto] Grotefend: Pocket book of the time calculation of the German Middle Ages and the modern times , 10th edition, ed. by Theodor Ulrich, Hahnsche Buchhandlung, Hanover 1960. ISBN 978-3775251778