Dionysius Exiguus in the context of "Christian Era"

The terms anno Domini (AD) and before Christ (BC) are used when designating years in the Gregorian and Julian 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". The form "BC" is specific to English, and equivalent abbreviations are used in other languages: the Latin form, rarely used in English, is ante Christum natum (ACN) or ante Christum (AC).

This calendar era takes as its epoch the traditionally reckoned year of the conception or birth 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 immediately follows the year 1 BC. This dating system was devised in 525 by the Eastern Roman monk Dionysius Exiguus but was not widely used until the 9th century. Modern scholars believe that the actual date of birth of Jesus was about 5 BC.

Year 1 BC was a common year starting on Friday or Saturday in the Julian calendar (the sources differ; see leap year error for further information) and a leap year starting on Thursday in the proleptic Julian calendar. It was also a leap year starting on Saturday in the Proleptic Gregorian calendar. At the time, it was known as the Year of the Consulship of Lentulus and Piso (or, less frequently, year 753 Ab urbe condita). The denomination 1 BC for this year has been used since the early medieval period when the Anno Domini calendar era became the prevalent method in Europe for naming years. The following year is AD 1 in the widely used Julian calendar and the proleptic Gregorian calendar, neither of which have a "year zero".

The Apostolic Canons, also called Apostolic canons (Latin: Canones apostolorum, "Canons of the Apostles"), Ecclesiastical Canons of the Same Holy Apostles, or Canons of the Holy Apostles, is a 4th-century Syrian Christian text. It is an Ancient Church Order, a collection of ancient ecclesiastical canons concerning the government and discipline of the Early Christian Church, allegedly written by the Apostles. This text is an appendix to the eighth book of the Apostolic Constitutions. Like the other Ancient Church Orders, the Apostolic Canons uses a pseudepigraphic form.

These eighty-five canons were approved by the Council in Trullo in 692 but were rejected by Pope Sergius I. In the Western Church only fifty of these canons circulated, translated in Latin by Dionysius Exiguus in about 500 AD, and included in the Western collections and afterwards in the Corpus Juris Canonici.

The Collectiones canonum Dionysianae (Latin for Dionysian collections of canons), also known as Collectio Dionysiana or Dionysiana Collectio ("Dionysian Collection"), are the several collections of ancient canons prepared by a Scythian monk, Dionysius 'the humble' (exiguus). They include the Collectio conciliorum Dionysiana I, the Collectio conciliorum Dionysiana II, and the Collectio decretalium Dionysiana. They are of the utmost importance for the development of the canon law tradition in the West.

Towards 500 a Scythian monk, known as Dionysius Exiguus, who had come to Rome after the death of Pope Gelasius (496), and who was well skilled in both Latin and Greek, undertook to bring out a more exact translation of the canons of the Greek church councils. In a second effort, he collected papal decretals from Siricius (384-89) to Anastasius II (496-98) included (, anterior therefore, to Pope Symmachus (498-514)). By order of Pope Hormisdas (514-23), Dionysius made a third collection, in which he included the original text of all the canons of the Greek councils, together with a Latin version of the same; but the preface alone has survived. Finally, he combined the first and second in one collection, which thus united the canons of the councils and the papal decretals; it is in this shape that the work of Dionysius has reached us.