Anno Domini - wikipedia Anno Domini `` AD '' and `` Before Christ '' redirect here. For other uses, see Anno Domini ( disambiguation ) and AD ( disambiguation ). Anno Domini inscription at a cathedral in Carinthia, Austria. The terms anno Domini ( AD ) and before Christ ( BC ) are used to label or number years in the Julian and Gregorian calendars. The term anno Domini is Medieval Latin 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 `` anno Domini nostri Jesu Christi '', which translates to `` in the year of our Lord Jesus Christ ''. This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus of Nazareth, with AD counting years from the start of this epoch, and BC denoting years before the start of the era. There is no year zero in this scheme, so the year AD 1 immediately follows the year 1 BC. This dating system was devised in 525 by Dionysius Exiguus of Scythia Minor, but was not widely used until after 800. The Gregorian calendar is the most widely used calendar in the world today. For decades, it has been the unofficial global standard, adopted in the pragmatic interests of international communication, transportation, and commercial integration, and recognized by international institutions such as the United Nations. Traditionally, English followed Latin usage by placing the `` AD '' abbreviation before the year number. However, BC is placed after the year number ( for example : AD 2018, but 68 BC ), which also preserves syntactic order. The abbreviation is also widely used after the number of a century or millennium, as in `` fourth century AD '' or `` second millennium AD '' ( although conservative usage formerly rejected such expressions ). Because 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. However, this would mean that the approximate 33 years commonly associated with the life of Jesus would neither be included in the BC nor the AD time scales. Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the Current or Common Era ( abbreviated as CE ), with the preceding years referred to as Before the Common or Current Era ( BCE ). Astronomical year numbering and ISO 8601 avoid words or abbreviations related to Christianity, but use the same numbers for AD years. Contents 1 History 1.1 Popularization 1.2 Change of year 2 Historical birth date of Jesus 3 Other eras 4 CE and BCE 5 No year zero / Start and end of a century 6 See also 7 Notes 8 References 8.1 Citations 8.2 Sources 9 External links History The Anno Domini dating system was devised in 525 by Dionysius Exiguus to enumerate the years in his Easter table. His system was to replace the Diocletian era that had been used in an old Easter table because he did not wish to continue the memory of a tyrant who persecuted Christians. The last year of the old table, Diocletian 247, was immediately followed by the first year of his table, AD 532. When he devised his table, Julian calendar years were identified by naming the consuls who held office that year -- he himself 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, 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. Among the sources of confusion are : In modern times, Incarnation is synonymous with the conception, but some ancient writers, such as Bede, 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. Two major theories are that Dionysius based his calculation on the Gospel of Luke, 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, or that Dionysius counted back 532 years from the first year of his new table. It is convenient to initiate a calendar not from the very day of an event but from the beginning of a cycle which occurs in close proximity. For example, the Islamic calendar begins not from the date of the Hijra, but rather weeks prior, on the first occurrence of the month of Muharram ( corresponding to 16 July 622 ). It has also been speculated by Georges Declercq 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 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. It was believed that, based on the Anno Mundi calendar, Jesus was born in the year 5500 ( or 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 resurrection and the end of the world but this date had already passed in the time of Dionysius. Popularization The Anglo - Saxon historian the Venerable Bede, who was familiar with the work of Dionysius Exiguus, used Anno Domini dating in his Ecclesiastical History of the English People, completed in 731. In this same history, he also used another Latin term, ante vero incarnationis dominicae tempus anno sexagesimo ( `` in fact in the 60th year before the time of the Lord 's incarnation '' ), 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, 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 on March 25 '' ( Annunciation style ). Statue of Charlemagne by Agostino Cornacchini ( 1725 ), at St. Peter 's Basilica, Vatican City. Charlemagne promoted the usage of the Anno Domini epoch throughout the Carolingian Empire. On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by the English cleric and scholar Alcuin in the late eighth century. Its endorsement by Emperor Charlemagne and his successors popularizing the use of the epoch and spreading it throughout the Carolingian Empire ultimately lies at the core of the system 's prevalence. According to the Catholic Encyclopedia, popes continued to date documents according to regnal years for some time, but usage of AD gradually became more common in Roman Catholic countries from the 11th to the 14th centuries. In 1422, Portugal became the last Western European country to switch to the system begun by Dionysius. Eastern Orthodox 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 the Venerable used the expression `` anno igitur ante incarnationem Dominicam '' ( so in the year before the Incarnation of the Lord ) twice. `` Anno an xpi nativitate '' ( in the year before the birth of Christ ) is found in 1474 in a work by a German monk. In 1627, the French Jesuit 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. Change of 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, 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 ( today in 1 BC ), i.e., notionally from the incarnation of Jesus. That first `` Annunciation style '' appeared in Arles 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 and survived there till 1750. From 25 December 753 AUC ( today in 1 BC ), i.e., notionally from the birth of Jesus. It was called `` Nativity style '' and had been spread by the Venerable 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 ( today in 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 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, starting in 754 AUC ( AD 1 ). That mos gallicanus ( French custom ) bound to a moveable feast 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. Historical birth date of Jesus See also : Date of birth of Jesus, Nativity of Jesus § Date of birth, and Chronology of Jesus § Historical birth date of Jesus 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 sketchy 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. Other eras Further information : Calendar era 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, imperial regnal year dating, and Creation dating. Although the last non-imperial consul, Basilius, was appointed in 541 by Emperor Justinian I, later emperors through Constans II ( 641 -- 668 ) were appointed consuls on the first 1 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 Alexandrian 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, years numbered from it, an Era of Incarnation, were exclusively used and are yet used, in Ethiopia. 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 used an era beginning with the birth of Abraham, dated in 2016 BC ( AD 1 = 2017 Anno Abrahami ). Spain and Portugal continued to date by the Era of the Caesars or Spanish Era, which began counting from 38 BC, well into the Middle Ages. In 1422, Portugal became the last Catholic country to adopt the Anno Domini system. The Era of Martyrs, which numbered years from the accession of Diocletian in 284, who launched the last yet most severe persecution of Christians, was used by the Church of Alexandria and is still used, officially, by the Coptic Orthodox and Coptic Catholic churches. It was also used by the Ethiopian church. Another system was to date from the crucifixion of Jesus Christ, which as early as Hippolytus and Tertullian was believed to have occurred in the consulate of the Gemini ( AD 29 ), which appears in some medieval manuscripts. CE and BCE Main article : Common Era 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 '' ( 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. For example, Cunningham and Starr ( 1998 ) write that `` B.C.E. / C.E.... do not presuppose faith in Christ and hence are more appropriate for interfaith dialog than the conventional B.C. / A.D. '' Upon its foundation, the Republic of China adopted the Minguo Era, but used the Western calendar for international purposes. The translated term was 西元 ( `` xī yuán '', `` Western Era '' ). Later, in 1949, the People 's Republic of China adopted 公元 ( gōngyuán, `` Common Era '' ) for all purposes domestic and foreign. No year zero / start and end of a century Further information : 0 ( year ), Astronomical year numbering, Millennium, and Century In the AD year numbering system, whether applied to the Julian or Gregorian calendars, AD 1 is preceded by 1 BC. There is no year `` 0 '' between them, so a new century begins in a year which has `` 01 '' as the final digits ( e.g., 1801, 1901, 2001 ). New millennia likewise are considered to have begun in 1001 and 2001. This is at odds with the much more common conception that centuries and millennia begin when the trailing digits are zeroes ( 1800, 1900, 2000, etc. ) ; for example, the worldwide celebration of the new millennium took place on New Year 's Eve 1999, when the year number ticked over to 2000. For computational reasons, astronomical year numbering and the ISO 8601 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 Ante Christum natum Calendar Common Era Holocene calendar Notes Jump up ^ The word `` anno '' is often capitalized, but this is considered incorrect by many authorities and either not mentioned in major dictionaries or only listed as an alternative. Wikipedia 's manual of style also prescribes lowercase. Jump up ^ The word `` before '' is often capitalized, but this is considered incorrect by many authorities and either not mentioned in major dictionaries or only listed as an alternative. Wikipedia 's manual of style also prescribes lowercase. Jump up ^ This convention comes from grammatical usage. Anno 500 means `` in the year 500 '' ; anno domini 500 means `` in the year 500 of Our Lord ''. Just as `` 500 in the year '' is not good English syntax, neither is 500 AD ; whereas `` AD 500 '' preserves syntactic order when translated. Jump up ^ To convert from a year BC to astronomical year numbering, reduce the absolute value of the year by 1, and prefix it with a negative sign ( unless the result is zero ). For years AD, omit the AD and prefix the number with a plus sign ( plus sign is optional if it is clear from the context that the year is after the year 0 ). References Citations Jump up ^ `` anno Domini ''. Collins English Dictionary. Jump up ^ `` anno Domini ''. American Heritage Dictionary. Houghton Mifflin Harcourt. Jump up ^ `` BC ''. Collins English Dictionary. Jump up ^ `` before Christ ''. American Heritage Dictionary. Houghton Mifflin Harcourt. Jump up ^ `` BC ''. Merriam Webster Online Dictionary. Jump up ^ `` Anno Domini ''. Merriam Webster Online Dictionary. Merriam - Webster. 2003. Retrieved 2011 - 10 - 04. Etymology : Medieval Latin, in the year of the Lord Jump up ^ `` Online Etymology Dictionary ''. Retrieved 2011 - 10 - 04. Jump up ^ Blackburn & Holford - Strevens 2003, p. 782 `` since AD stands for anno Domini, ' in the year of ( Our ) Lord ' '' ^ Jump up to : Teresi, Dick ( July 1997 ). `` Zero ''. The Atlantic. ^ Jump up to : Blackburn & Holford - Strevens 2003, pp. 778 -- 9. Jump up ^ Eastman, Allan. `` A Month of Sundays ''. Date and Time. Archived from the original on 2010 - 05 - 06. Retrieved 2010 - 05 - 04. Jump up ^ Chicago Manual of Style 2010, pp. 476 -- 7 ; Goldstein 2007, p. 6. Jump up ^ Chicago Manual of Style, 1993, p. 304. Jump up ^ Donald P. Ryan, ( 2000 ), 15. Jump up ^ Blackburn & Holford - Strevens 2003, p. 767. Jump up ^ Nineteen year cycle of Dionysius Introduction and First Argumentum. Jump up ^ Blackburn & Holford - Strevens 2003, p. 778. Jump up ^ Tøndering, Claus, The Calendar FAQ : Counting years Jump up ^ Mosshammer, Alden A ( 2009 ). The Easter Computus and the Origins of the Christian Era. Oxford. p. 347. Jump up ^ F.A. Shamsi, `` The Date of Hijrah '', Islamic Studies 23 ( 1984 ) : 189 - 224, 289 - 323 ( JSTOR link 1 + JSTOR link 2 ). Jump up ^ Declercq, Georges, `` Anno Domini. The Origins of the Christian Era '' Turnhout, Belgium, 2000 Jump up ^ Wallraff, Martin : Julius Africanus und die Christliche Weltchronik. Walter de Gruyter, 2006 Jump up ^ Mosshammer, Alden A. : The Easter Computus and the Origins of the Christian Era. Oxford University Press, 2009, p. 254, p. 270, p. 328 Jump up ^ Declercq, Georges : Anno Domini. The Origins of the Christian Era. Turnhout Belgium. 2000 Jump up ^ Bede 731, Book 1, Chapter 2, first sentence. Jump up ^ Blackburn & Holford - Strevens 2003, p. 881. ^ Jump up to : Patrick, 1908 Jump up ^ `` General Chronology ''. New Advent Catholic Encyclopedia. Vol III. New York : Robert Appleton Company. 1908. Retrieved 2011 - 10 - 25. Jump up ^ Werner Rolevinck in Fasciculus temporum ( 1474 ) used Anno an xpi nativitatem ( in the... ( th ) year before the birth of Christ ) for all years between creation and Jesus. `` xpi '' is the Greek χρι in Latin letters, which is an abbreviation for Christi. This phrase appears upside down in the centre of recto folios ( right hand pages ). From Jesus to Pope Sixtus IV he usually used Anno Christi or its abbreviated form Anno xpi ( on verso folios -- left hand pages ). He used Anno mundi alongside all of these terms for all years. Jump up ^ Steel, Duncan ( 2000 ). Marking time : the epic quest to invent the perfect calendar. p. 114. ISBN 978 - 0 - 471 - 29827 - 4. Retrieved 2010 - 06 - 01. Jump up ^ Hunt, Lynn Avery ( 2008 ). Measuring time, making history. p. 33. ISBN 978 - 963 - 9776 - 14 - 2. Retrieved 2010 - 06 - 01. Jump up ^ Petau, Denis ( 1758 ). search for `` ante Christum '' in a 1748 reprint of a 1633 abridgement entitled Rationarium temporum by Denis Petau. Retrieved 2010 - 06 - 01. Jump up ^ C.R. Cheney, A Handbook of Dates, for students of British history, Cambridge University Press, 1945 -- 2000, pp. 8 -- 14. Jump up ^ Dunn, James DG ( 2003 ). `` Jesus Remembered ''. Eerdmans Publishing : 324. Jump up ^ Doggett 1992, p579 : `` Although scholars generally believe that Christ was born some years before AD 1, the historical evidence is too sketchy to allow a definitive dating ''. Jump up ^ 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 ISBN 0 - 931464 - 50 - 1 pp. 113 -- 129 Jump up ^ New Testament History by Richard L. Niswonger 1992 ISBN 0 - 310 - 31201 - 9 pp. 121 -- 124 Jump up ^ Roger S. Bagnall and Klaas A. Worp, Chronological Systems of Byzantine Egypt, Leiden, Brill, 2004. Jump up ^ Alfred von Gutschmid, Kleine Schriften, F. Ruehl, Leipzig, 1889, p. 433. Jump up ^ Johannes Kepler ( 1615 ). Joannis Keppleri Eclogae chronicae : ex epistolis doctissimorum aliquot virorum & suis mutuis, quibus examinantur tempora nobilissima : 1. Herodis Herodiadumque, 2. baptismi & ministerii Christi annorum non plus 2 1 / 4, 3. passionis, mortis et resurrectionis Dn. N. Iesu Christi, anno aerae nostrae vulgaris 31. non, ut vulgo 33., 4. belli Iudaici, quo funerata fuit cum Ierosolymis & Templo Synagoga Iudaica, sublatumque Vetus Testamentum. Inter alia & commentarius in locum Epiphanii obscurissimum de cyclo veteri Iudaeorum. ( in Latin ). Francofurti : Tampach. Retrieved 2011 - 05 - 18. anno aerae nostrae vulgaris Jump up ^ Kepler, Johann ; Vlacq, Adriaan ( 1635 ). Ephemerides of the Celestiall Motions, for the Yeers of the Vulgar Era 1633... Retrieved 2011 - 05 - 18. Jump up ^ Sliter, Robert ( 1652 ). A celestiall glasse, or, Ephemeris for the year of the Christian era 1652 being the bissextile or leap - year : contayning the lunations, planetary motions, configurations & ecclipses for this present year... : with many other things very delightfull and necessary for most sorts of men : calculated exactly and composed for... Rochester. London : Printed for the Company of Stationers. Jump up ^ The History of the Works of the Learned. 10. London : Printed for H. Rhodes. January 1708. p. 513. Retrieved 2011 - 05 - 18. Jump up ^ BBC Team ( 8 February 2005 ). `` History of Judaism 63BCE -- 1086CE ''. BBC Religion & Ethics. British Broadcasting Corporation. Archived from the original on 2011 - 05 - 13. Retrieved 2011 - 05 - 18. Year 1 : CE -- What is nowadays called the ' Current Era ' traditionally begins with the birth of a Jewish teacher called Jesus. His followers came to believe he was the promised Messiah and later split away from Judaism to found Christianity Jump up ^ Raphall, Morris Jacob ( 1856 ). Post-Biblical History of The Jews. Moss & Brother. Archived from the original on 11 May 2011. Retrieved 2011 - 05 - 18. The term common era does not appear in this book ; the term Christian era ( lowercase ) does appear a number of times. Nowhere in the book is the abbreviation explained or expanded directly. Jump up ^ Robinson, B.A. ( 20 April 2009 ). `` Justification of the use of `` CE '' & `` BCE '' to identify dates. Trends ``. ReligiousTolerance.org. Jump up ^ William Safire ( 17 August 1997 ). `` On Language : B.C. / A.D. or B.C.E. / C.E. ? ''. The New York Times Magazine. Jump up ^ Cunningham, ed. by Philip A. ( 2004 ). Pondering the Passion : what 's at stake for Christians and Jews ?. Lanham, Md. ( u.a. ) : Rowman & Littlefield. p. 193. ISBN 978 - 0742532182. CS1 maint : Extra text : authors list ( link ) Jump up ^ Doggett, 1992, p. 579 Sources Abate, Frank R. ( ed. ) ( 1997 ). Oxford Pocket Dictionary and Thesaurus ( American ed. ). New York : Oxford University Press. ISBN 0 - 19 - 513097 - 9. CS1 maint : Extra text : authors list ( link ) Goldstein, Norm, ed. ( 2007 ). Associated Press Style Book. New York : Basic Books. ISBN 0 - 465 - 00489 - X. Bede. ( 731 ). Historiam ecclesiasticam gentis Anglorum. Accessed 2007 - 12 - 07. Chicago Manual of Style ( 2nd ed. ). University of Chicago. 1993. ISBN 0 - 226 - 10389 - 7. Chicago Manual of Style ( 16th ed. ). University of Chicago. 2010. ISBN 0 - 226 - 10420 - 6. Blackburn, Bonnie ; Holford - Strevens, Leofranc ( 2003 ). The Oxford companion to the Year : An exploration of calendar customs and time - reckoning. Oxford University Press. ISBN 0 - 19 - 214231 - 3. Corrected reprinting of original 1999 edition. Cunningham, Philip A ; Starr, Arthur F ( 1998 ). Sharing Shalom : A Process for Local Interfaith Dialogue Between Christians and Jews. Paulist Press. ISBN 0 - 8091 - 3835 - 2. Declercq, Georges ( 2000 ). Anno Domini : The origins of the Christian era. Turnhout : Brepols. ISBN 2 - 503 - 51050 - 7. ( 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 ). `` Calendars '' ( Ch. 12 ), in P. Kenneth Seidelmann ( Ed. ) Explanatory supplement to the astronomical almanac. Sausalito, CA : University Science Books. ISBN 0 - 935702 - 68 - 7. Patrick, J. ( 1908 ). `` General Chronology ''. In The Catholic Encyclopedia. New York : Robert Appleton Company. Retrieved 2008 - 07 - 16 from New Advent : http://www.newadvent.org/cathen/03738a.htm Richards, E.G. ( 2000 ). Mapping Time. Oxford : Oxford University Press. ISBN 0 - 19 - 286205 - 7. Riggs, John ( January 2003 ). `` Whatever happened to B.C. and A.D., and why ? ''. United Church News. Retrieved 2005 - 12 - 19. Ryan, Donald P. ( 2000 ). The Complete Idiot 's Guide to Biblical Mysteries. Alpha Books. p. 15. ISBN 0 - 02 - 863831 - X. External links Look up AD or Anno Domini in Wiktionary, the free dictionary. 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Question: when does it change from bc to ad
Answer: conception or birth of Jesus of Nazareth