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The terms (AD) and before Christ (BC) are used when designating years in the Gregorian and Julian calendars. The term is
Medieval Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Church, Roman Catholic Western Europe during the Middle Ages. It was also the administrative language in the former Western Roman Empire, Roman Provinces of Mauretania, Numidi ...
and means "in the year of the Lord" but is often presented using "our Lord" instead of "the Lord", taken from the full original phrase "", which translates to "in the year of our Lord
Jesus Christ Jesus (AD 30 or 33), also referred to as Jesus Christ, Jesus of Nazareth, and many Names and titles of Jesus in the New Testament, other names and titles, was a 1st-century Jewish preacher and religious leader. He is the Jesus in Chris ...
". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
form, rarely used in English, is (ACN) or (AC). This
calendar era A calendar era is the period of time elapsed since one '' epoch'' of a calendar and, if it exists, before the next one. For example, the current year is numbered in the Gregorian calendar, which numbers its years in the Western Christian era ...
takes as its
epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...
the traditionally reckoned year of the conception or
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...
of Jesus. Years ''AD'' are counted forward since that epoch and years ''BC'' are counted backward from the epoch. There is no year zero in this scheme; thus the year
AD 1 The 0s began on January 1, AD 1 and ended on December 31, AD 9, covering the first nine years of the Common Era. In Europe, the 0s saw the continuation of conflict between the Roman Empire and Germanic tribes in the Early Imperial campaigns ...
immediately follows the year
1 BC Year 1 BC was a common year starting on Friday or Common year starting on Saturday, Saturday in the Julian calendar (the sources differ; see Julian calendar#Leap year error, leap year error for further information) and a leap year starting on T ...
. This dating system was devised in 525 by
Dionysius Exiguus Dionysius Exiguus (Latin for "Dionysius the Humble"; Greek: Διονύσιος; – ) was a 6th-century Eastern Roman monk born in Scythia Minor. He was a member of a community of Scythian monks concentrated in Tomis (present-day Constanț ...
but was not widely used until the 9th century. Modern scholars believe that the actual
date of birth of Jesus The date of the birth of Jesus is not stated in the gospels or in any Historical Jesus, historical sources and the evidence is too incomplete to allow for consistent dating. However, most biblical scholars and ancient historians believe that hi ...
was about 5 BC. D. A. Carson, Douglas J. Moo & Leon Morris. (1992). ''An Introduction to the New Testament'', 54, 56. Grand Rapids, MI: Zondervan Publishing House. Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the
Common Era Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the ...
(abbreviated as CE), with the preceding years referred to as Before the Common Era (BCE). Astronomical year numbering and
ISO 8601 ISO 8601 is an international standard covering the worldwide exchange and communication of date and time-related data. It is maintained by the International Organization for Standardization (ISO) and was first published in 1988, with updates in ...
do not use words or abbreviations related to Christianity, but use the same numbers for AD years (but not for BC years since the astronomical year 0 is 1 BC).


Usage

Traditionally, English follows Latin usage by placing the "AD" abbreviation before the year number, though it is also found after the year. In contrast, "BC" is always placed after the year number (for example: 70 BC but AD 70), which preserves syntactic order. The abbreviation "AD" is also widely used after the number of a century or
millennium A millennium () is a period of one thousand years, one hundred decades, or ten centuries, sometimes called a kiloannum (ka), or kiloyear (ky). Normally, the word is used specifically for periods of a thousand years that begin at the starting ...
, as in "fourth century AD" or "second millennium AD" (although conservative usage formerly rejected such expressions). Since "BC" is the English abbreviation for ''Before Christ'', it is sometimes incorrectly concluded that AD means ''After Death'' (i.e., after the death of Jesus), which would mean that the approximately 33 years commonly associated with the life of Jesus would be included in neither the BC nor the AD time scales.


History

The ''anno Domini'' dating system was devised in 525 by
Dionysius Exiguus Dionysius Exiguus (Latin for "Dionysius the Humble"; Greek: Διονύσιος; – ) was a 6th-century Eastern Roman monk born in Scythia Minor. He was a member of a community of Scythian monks concentrated in Tomis (present-day Constanț ...
to enumerate years in his Easter table. His system was to replace the Diocletian era that had been used in older Easter tables, as he did not wish to continue the memory of a tyrant who persecuted Christians. The last year of the old table, Diocletian Anno Martyrium 247, was immediately followed by the first year of his table, anno Domini 532. When Dionysius devised his table,
Julian calendar The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year (without exception). The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts ...
years were identified by naming the
consuls A consul is an official representative of a government who resides in a foreign country to assist and protect citizens of the consul's country, and to promote and facilitate commercial and diplomatic relations between the two countries. A consu ...
who held office that year—Dionysius stated that the "present year" was "the consulship of Probus Junior", which was 525 years "since the incarnation of our Lord Jesus Christ". Thus, Dionysius implied that Jesus' incarnation occurred 525 years earlier, without stating the specific year during which his birth or conception occurred. "However, nowhere in his exposition of his table does Dionysius relate his epoch to any other dating system, whether consulate,
Olympiad An olympiad (, ''Olympiás'') is a period of four years, particularly those associated with the Ancient Olympic Games, ancient and Olympic Games, modern Olympic Games. Although the ancient Olympics were established during Archaic Greece, Greece ...
, year of the world, or regnal year of Augustus; much less does he explain or justify the underlying date." Bonnie J. Blackburn and Leofranc Holford-Strevens briefly present arguments for 2 BC, 1 BC, or AD 1 as the year Dionysius intended for the Nativity or
incarnation Incarnation literally means ''embodied in flesh'' or ''taking on flesh''. It is the Conception (biology), conception and the embodiment of a deity or spirit in some earthly form or an Anthropomorphism, anthropomorphic form of a god. It is used t ...
. Among the sources of confusion are: * In modern times,
incarnation Incarnation literally means ''embodied in flesh'' or ''taking on flesh''. It is the Conception (biology), conception and the embodiment of a deity or spirit in some earthly form or an Anthropomorphism, anthropomorphic form of a god. It is used t ...
is synonymous with the conception, but some ancient writers, such as
Bede Bede (; ; 672/326 May 735), also known as Saint Bede, Bede of Jarrow, the Venerable Bede, and Bede the Venerable (), was an English monk, author and scholar. He was one of the most known writers during the Early Middle Ages, and his most f ...
, considered incarnation to be synonymous with the Nativity. * The civil or consular year began on 1 January, but the Diocletian year began on 29 August (30 August in the year before a Julian leap year). * There were inaccuracies in the lists of consuls. * There were confused summations of emperors' regnal years. It is not known how Dionysius established the year of Jesus's birth. One theory is that Dionysius based his calculation on the
Gospel of Luke The Gospel of Luke is the third of the New Testament's four canonical Gospels. It tells of the origins, Nativity of Jesus, birth, Ministry of Jesus, ministry, Crucifixion of Jesus, death, Resurrection of Jesus, resurrection, and Ascension of ...
, which states that Jesus was "about thirty years old" shortly after "the fifteenth year of the reign of Tiberius Caesar", and hence subtracted thirty years from that date. This method was probably the one used by ancient historians such as
Tertullian Tertullian (; ; 155 – 220 AD) was a prolific Early Christianity, early Christian author from Roman Carthage, Carthage in the Africa (Roman province), Roman province of Africa. He was the first Christian author to produce an extensive co ...
, Eusebius or Epiphanius, all of whom agree that Jesus was born in 2 BC, probably following this statement of Jesus' age (i.e. subtracting thirty years from AD 29). Another major theory asserts that Dionysius counted back 532 years from the first year of his new table, following an 532-year cycle established by the astronomical computations of Victorius of Aquitaine (the dates for Easter repeat every 532 years). Alternatively, Dionysius may have used an earlier unknown source, as the earlier Chronograph of 354 states that Jesus was born during the consulship of Caesar and Paullus (AD 1). It has also been speculated by Georges DeclercqDeclercq, Georges(2000). "Anno Domini. The Origins of the Christian Era" Turnhout, Belgium, that Dionysius' desire to replace Diocletian years with a calendar based on the incarnation of Christ was intended to prevent people from believing the imminent end of the world. At the time, it was believed by some that the resurrection of the dead and end of the world would occur 500 years after the birth of Jesus. The old '' Anno Mundi'' calendar theoretically commenced with the creation of the world based on information in the
Old Testament The Old Testament (OT) is the first division of the Christian biblical canon, which is based primarily upon the 24 books of the Hebrew Bible, or Tanakh, a collection of ancient religious Hebrew and occasionally Aramaic writings by the Isr ...
. It was believed that, based on the ''Anno Mundi'' calendar, Jesus was born in the year 5500 (5500 years after the world was created) with the year 6000 of the ''Anno Mundi'' calendar marking the end of the world. ''Anno Mundi'' 6000 (approximately AD 500) was thus equated with the end of the world but this date had already passed in the time of Dionysius. The "''Historia Brittonum''" attributed to Nennius written in the 9th century makes extensive use of the Anno Passionis (AP) dating system which was in common use as well as the newer AD dating system. The AP dating system took its start from 'The Year of The Passion'. It is generally accepted by experts there is a 27-year difference between AP and AD reference. The date of birth of Jesus of Nazareth is not stated in the gospels or in any secular text, but most scholars assume a date of birth between 6 BC and 4 BC. The historical evidence is too fragmentary to allow a definitive dating, but the date is estimated through two different approaches—one by analyzing references to known historical events mentioned in the Nativity accounts in the Gospels of Luke and Matthew and the second by working backwards from the estimation of the start of the
ministry of Jesus The ministry of Jesus, in the canonical gospels, begins with Baptism of Jesus, his baptism near the River Jordan by John the Baptist, and ends in Jerusalem in Christianity, Jerusalem in Judea, following the Last Supper with his Disciple (Chri ...
. Paul L. Maier "The Date of the Nativity and Chronology of Jesus" in ''Chronos, kairos, Christos: nativity and chronological studies'' by Jerry Vardaman, Edwin M. Yamauchi 1989 pp. 113–29''New Testament History'' by Richard L. Niswonger 1992 pp. 121–24


Popularization

The
Anglo-Saxon The Anglo-Saxons, in some contexts simply called Saxons or the English, were a Cultural identity, cultural group who spoke Old English and inhabited much of what is now England and south-eastern Scotland in the Early Middle Ages. They traced t ...
historian
Bede Bede (; ; 672/326 May 735), also known as Saint Bede, Bede of Jarrow, the Venerable Bede, and Bede the Venerable (), was an English monk, author and scholar. He was one of the most known writers during the Early Middle Ages, and his most f ...
, who was familiar with the work of Dionysius Exiguus, used ''anno Domini'' dating in his '' Ecclesiastical History of the English People'', which he completed in AD 731. In the ''History'' he also used the
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
phrase ''ante ..incarnationis dominicae tempus anno sexagesimo'' ("in the sixtieth year before the time of the Lord's incarnation"), which is equivalent to the English "before Christ", to identify years before the first year of this era. Both Dionysius and Bede regarded ''anno Domini'' as beginning at the incarnation of
Jesus Christ Jesus (AD 30 or 33), also referred to as Jesus Christ, Jesus of Nazareth, and many Names and titles of Jesus in the New Testament, other names and titles, was a 1st-century Jewish preacher and religious leader. He is the Jesus in Chris ...
, but "the distinction between Incarnation and Nativity was not drawn until the late 9th century, when in some places the Incarnation epoch was identified with Christ's conception, i. e., the
Annunciation The Annunciation (; ; also referred to as the Annunciation to the Blessed Virgin Mary, the Annunciation of Our Lady, or the Annunciation of the Lord; ) is, according to the Gospel of Luke, the announcement made by the archangel Gabriel to Ma ...
on March 25" ("Annunciation style" dating). On the continent of Europe, ''anno Domini'' was introduced as the era of choice of the
Carolingian Renaissance The Carolingian Renaissance was the first of three medieval renaissances, a period of cultural activity in the Carolingian Empire. Charlemagne's reign led to an intellectual revival beginning in the 8th century and continuing throughout the 9th ...
by the English cleric and scholar
Alcuin Alcuin of York (; ; 735 – 19 May 804), also called Ealhwine, Alhwin, or Alchoin, was a scholar, clergyman, poet, and teacher from York, Northumbria. He was born around 735 and became the student of Ecgbert of York, Archbishop Ecgbert at Yor ...
in the late eighth century. Its endorsement by Emperor
Charlemagne Charlemagne ( ; 2 April 748 – 28 January 814) was List of Frankish kings, King of the Franks from 768, List of kings of the Lombards, King of the Lombards from 774, and Holy Roman Emperor, Emperor of what is now known as the Carolingian ...
and his successors popularizing the use of the epoch and spreading it throughout the
Carolingian Empire The Carolingian Empire (800–887) was a Franks, Frankish-dominated empire in Western and Central Europe during the Early Middle Ages. It was ruled by the Carolingian dynasty, which had ruled as List of Frankish kings, kings of the Franks since ...
ultimately lies at the core of the system's prevalence. According to the
Catholic Encyclopedia ''The'' ''Catholic Encyclopedia: An International Work of Reference on the Constitution, Doctrine, Discipline, and History of the Catholic Church'', also referred to as the ''Old Catholic Encyclopedia'' and the ''Original Catholic Encyclopedi ...
, popes continued to date documents according to regnal years for some time, but usage of AD gradually became more common in Catholic countries from the 11th to the 14th centuries.Patrick, 1908 In 1422,
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
became the last Western European country to switch to the system begun by Dionysius.
Eastern Orthodox Eastern Orthodoxy, otherwise known as Eastern Orthodox Christianity or Byzantine Christianity, is one of the three main Branches of Christianity, branches of Chalcedonian Christianity, alongside Catholic Church, Catholicism and Protestantism ...
countries only began to adopt AD instead of the Byzantine calendar in 1700 when Russia did so, with others adopting it in the 19th and 20th centuries. Although ''anno Domini'' was in widespread use by the 9th century, the term "Before Christ" (or its equivalent) did not become common until much later. Bede used the expression ''"anno ..ante incarnationem Dominicam"'' (in the year before the incarnation of the Lord) twice. ''"Anno ante Christi nativitatem"'' (in the year before the birth of Christ) is found in 1474 in a work by a German monk. In 1627, the French
Jesuit The Society of Jesus (; abbreviation: S.J. or SJ), also known as the Jesuit Order or the Jesuits ( ; ), is a religious order (Catholic), religious order of clerics regular of pontifical right for men in the Catholic Church headquartered in Rom ...
theologian Denis Pétau (Dionysius Petavius in Latin), with his work ''De doctrina temporum'', popularized the usage ''ante Christum'' (Latin for "Before Christ") to mark years prior to AD.


New year

When the reckoning from Jesus' incarnation began replacing the previous dating systems in western Europe, various people chose different Christian feast days to begin the year: Christmas,
Annunciation The Annunciation (; ; also referred to as the Annunciation to the Blessed Virgin Mary, the Annunciation of Our Lady, or the Annunciation of the Lord; ) is, according to the Gospel of Luke, the announcement made by the archangel Gabriel to Ma ...
, or Easter. Thus, depending on the time and place, the year number changed on different days in the year, which created slightly different styles in chronology: * From 25 March 753 AUC (1 BC), i.e., notionally from the incarnation of Jesus. That first "Annunciation style" appeared in
Arles Arles ( , , ; ; Classical ) is a coastal city and Communes of France, commune in the South of France, a Subprefectures in France, subprefecture in the Bouches-du-Rhône Departments of France, department of the Provence-Alpes-Côte d'Azur Reg ...
at the end of the 9th century then spread to Burgundy and northern Italy. It was not commonly used and was called ''calculus pisanus'' since it was adopted in
Pisa Pisa ( ; ) is a city and ''comune'' (municipality) in Tuscany, Central Italy, straddling the Arno just before it empties into the Ligurian Sea. It is the capital city of the Province of Pisa. Although Pisa is known worldwide for the Leaning Tow ...
and survived there until 1750. * From 25 December 753 AUC (1 BC), i.e., notionally from the birth of Jesus. It was called "Nativity style" and had been spread by Bede together with the ''anno Domini'' in the early Middle Ages. That reckoning of the Year of Grace from Christmas was used in France, England and most of western Europe (except Spain) until the 12th century (when it was replaced by Annunciation style) and in Germany until the second quarter of the 13th century. * From 25 March 754 AUC (AD 1). That second "Annunciation style" may have originated in Fleury Abbey in the early 11th century, but it was spread by the Cistercians.
Florence Florence ( ; ) is the capital city of the Italy, Italian region of Tuscany. It is also the most populated city in Tuscany, with 362,353 inhabitants, and 989,460 in Metropolitan City of Florence, its metropolitan province as of 2025. Florence ...
adopted that style in opposition to that of Pisa, so it got the name of ''calculus florentinus''. It soon spread in France and also in England where it became common in the late 12th century and lasted until 1752. * From Easter. That ''mos gallicanus'' (French custom) bound to a
moveable feast A moveable feast is an observance in a Christian liturgical calendar which occurs on different dates in different years. It is the complement of a fixed feast, an annual celebration that is held on the same calendar date every year, such as Chri ...
was introduced in France by king Philip Augustus (r. 1180–1223), maybe to establish a new style in the provinces reconquered from England. However, it never spread beyond the ruling élite. With these various styles, the same day could, in some cases, be dated in 1099, 1100 or 1101.


Other Christian and European eras

During the first six centuries of what would come to be known as the Christian era, European countries used various systems to count years. Systems in use included
consular dating A consul is an official representative of a government who resides in a foreign country to assist and protect citizens of the consul's country, and to promote and facilitate commercial and diplomatic relations between the two countries. A consu ...
, imperial regnal year dating, and Creation dating. Although the last non-imperial consul, Basilius, was appointed in 541 by Emperor
Justinian I Justinian I (, ; 48214 November 565), also known as Justinian the Great, was Roman emperor from 527 to 565. His reign was marked by the ambitious but only partly realized ''renovatio imperii'', or "restoration of the Empire". This ambition was ...
, later emperors through to Constans II (641–668) were appointed consuls on the first of January after their accession. All of these emperors, except Justinian, used imperial post-consular years for the years of their reign, along with their regnal years. Long unused, this practice was not formally abolished until Novell XCIV of the law code of Leo VI did so in 888. Another calculation had been developed by the
Alexandria Alexandria ( ; ) is the List of cities and towns in Egypt#Largest cities, second largest city in Egypt and the List of coastal settlements of the Mediterranean Sea, largest city on the Mediterranean coast. It lies at the western edge of the Nile ...
n monk Annianus around the year AD 400, placing the Annunciation on 25 March AD 9 (Julian)—eight to ten years after the date that Dionysius was to imply. Although this incarnation was popular during the early centuries of the
Byzantine Empire The Byzantine Empire, also known as the Eastern Roman Empire, was the continuation of the Roman Empire centred on Constantinople during late antiquity and the Middle Ages. Having survived History of the Roman Empire, the events that caused the ...
, years numbered from it, an ''Era of Incarnation'', were exclusively used and are still used in
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
. This accounts for the seven- or eight-year discrepancy between the Gregorian and Ethiopian calendars. Byzantine chroniclers like Maximus the Confessor, George Syncellus, and Theophanes dated their years from Annianus' creation of the world. This era, called '' Anno Mundi'', "year of the world" (abbreviated AM), by modern scholars, began its first year on 25 March 5492 BC. Later Byzantine chroniclers used ''Anno Mundi'' years from 1 September 5509 BC, the Byzantine Era. No single ''Anno Mundi'' epoch was dominant throughout the Christian world. Eusebius of Caesarea in his ''
Chronicle A chronicle (, from Greek ''chroniká'', from , ''chrónos'' – "time") is a historical account of events arranged in chronological order, as in a timeline. Typically, equal weight is given for historically important events and local events ...
'' used an era beginning with the birth of
Abraham Abraham (originally Abram) is the common Hebrews, Hebrew Patriarchs (Bible), patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father who began the Covenant (biblical), covenanta ...
, dated in 2016 BC (AD 1 = 2017 Anno Abrahami). Spain and Portugal continued to date by the Spanish Era (also called Era of the Caesars), which began counting from 38 BC, well into the Middle Ages. In 1422,
Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...
became the last Catholic country to adopt the ''anno Domini'' system. The Era of Martyrs, which numbered years from the accession of
Diocletian Diocletian ( ; ; ; 242/245 – 311/312), nicknamed Jovius, was Roman emperor from 284 until his abdication in 305. He was born Diocles to a family of low status in the Roman province of Dalmatia (Roman province), Dalmatia. As with other Illyri ...
in 284, who launched the most severe persecution of Christians, was used by the Church of Alexandria and is still officially used by the Coptic Orthodox and Coptic Catholic churches. It was also used by the
Ethiopian Ethiopians are the native inhabitants of Ethiopia, as well as the global diaspora of Ethiopia. Ethiopians constitute several component ethnic groups, many of which are closely related to ethnic groups in neighboring Eritrea and other parts of ...
and Eritrean churches. Another system was to date from the
crucifixion of Jesus The crucifixion of Jesus was the death of Jesus by being crucifixion, nailed to a cross.The instrument of Jesus' crucifixion, instrument of crucifixion is taken to be an upright wooden beam to which was added a transverse wooden beam, thus f ...
, which as early as Hippolytus and
Tertullian Tertullian (; ; 155 – 220 AD) was a prolific Early Christianity, early Christian author from Roman Carthage, Carthage in the Africa (Roman province), Roman province of Africa. He was the first Christian author to produce an extensive co ...
was believed to have occurred in the consulate of the Gemini (AD 29), which appears in some
medieval In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of World history (field), global history. It began with the fall of the West ...
manuscripts.


CE and BCE

Alternative names for the ''anno Domini'' era include ''vulgaris aerae'' (found 1615 in Latin), "Vulgar Era" (in English, as early as 1635), "Christian Era" (in English, in 1652), "
Common Era Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the ...
" (in English, 1708), and "Current Era". Since 1856, the alternative abbreviations CE and BCE (sometimes written C.E. and B.C.E.) are sometimes used in place of AD and BC. The "Common/Current Era" ("CE") terminology is often preferred by those who desire a term that does not explicitly make religious references but still uses the same epoch as the ''anno Domini'' notation. For example, Cunningham and Starr (1998) write that "B.C.E./C.E. ��do not presuppose faith in
Christ Jesus ( AD 30 or 33), also referred to as Jesus Christ, Jesus of Nazareth, and many other names and titles, was a 1st-century Jewish preacher and religious leader. He is the Jesus in Christianity, central figure of Christianity, the M ...
and hence are more appropriate for interfaith dialog than the conventional B.C./A.D." Upon its foundation, the
Republic of China Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...
adopted the Minguo Era but used the Western calendar for international purposes. The translated term was (). Later, in 1949, the People's Republic of China adopted () for all purposes domestic and foreign.


No year zero: start and end of a century

In the AD year numbering system, whether applied to the Julian or
Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...
s, AD 1 is immediately preceded by 1 BC, with nothing in between them (there was no year zero). There are debates as to whether a new decade, century, or millennium begins on a year ending in zero or one. For computational reasons, astronomical year numbering and the
ISO 8601 ISO 8601 is an international standard covering the worldwide exchange and communication of date and time-related data. It is maintained by the International Organization for Standardization (ISO) and was first published in 1988, with updates in ...
standard designate years so that AD 1 = year 1, 1 BC = year 0, 2 BC = year −1, etc. In common usage, ancient dates are expressed in the Julian calendar, but ISO 8601 uses the Gregorian calendar and astronomers may use a variety of time scales depending on the application. Thus dates using the year 0 or negative years may require further investigation before being converted to BC or AD.


See also

* Astronomical year numbering *
Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...
*
Calendar A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A calendar date, date is the designation of a single and specific day within such a system. A calendar is ...
*
Holocene calendar The Holocene calendar, also known as the Holocene Era or Human Era (HE), is a year numbering system that adds exactly 10,000 years to the currently dominant ( AD/BC or CE/BCE) numbering scheme, placing its first year near the beginning of the ...


Notes


References


Citations


Sources

* * Bede. (731)
''Historiam ecclesiasticam gentis Anglorum''
. Retrieved 2007-12-07. * * * Corrected reprinting of original 1999 edition. * * (despite beginning with 2, it is English) * Declercq, G. "Dionysius Exiguus and the Introduction of the Christian Era". ''Sacris Erudiri'' 41 (2002): 165–246. An annotated version of part of ''Anno Domini''. * Doggett. (1992)

(Ch. 12), in P. Kenneth Seidelmann (Ed.) ''Explanatory supplement to the astronomical almanac.'' Sausalito, CA: University Science Books. . * * Patrick, J. (1908)

. In ''The Catholic Encyclopedia''. New York: Robert Appleton Company. Retrieved 2008-07-16 from New Advent

* * *


External links


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