Anno Domini ("In the year of our Lord"), more completely Anno Domini Nostri Jesu Christi ("In the year of our Lord Jesus Christ"), dating was not the initial choice of Christians in the Mediterranean world; actually, it was not adopted in Western Europe until after the end of the Western Roman Empire. Like the other inhabitants of the Roman Empire, early Christians used one of several methods to indicate a specific year — and it was not uncommon for more than one to be used in the same document. This redundancy, in fact, allows historians to construct parallel regnal lists for many kingdoms and polities by comparing chronicles from different regions which include the same rulers. The AD system was developed by a monk named Dionysius Exiguus (a Scythian) in Rome in 525, as an outcome of his work on calculating the date of Easter. Byzantine chroniclers like Theophanes continued to date each year in their world chronicles on a different and much more popular Judaeo-Christian basis — from the notional creation of the World as calculated by Christian scholars in the first five centuries of the Christian era. These eras, sometimes called Anno Mundi, "year of the world" (abbreviated AM), by modern scholars, had their own disagreements. The first historian or chronicler to use AD as his primary dating mechanism was Victor of Tonnenna, an African chronicler of the 7th century. A few generations later, the Anglo-Saxon monk Bede, who was familiar with the work of Dionysius, also used Anno Domini dating in his Ecclesiastical History of the English People, finished in 731. Bede was different from historians working in more important places in two ways: First, he was in Northumbria, outside the bounds of the later Roman Empire. Unlike the Mediterranean-focused countries of Italy, France, and Spain, his people had little knowledge of or interest in who the Roman Emperor was in any particular year. Second, he was confronted with the problem of seven Anglo-Saxon kingdoms and their overlapping regnal years. He had also previously written a chronicle going back to Creation, so he had the numbers at his fingertips. He adopted AD dating as a way of keeping track of the Anglo-Saxon kingdoms and trying to bring their dates into line with the fragmentary evidence he had for imperial regnal years. In this same history, he was the first to use BC ("Before Christ") and established the standard for historians of no year zero, even though he used zero in his computus. On the continent of Europe, AD was first used as the dominant dating system by Charlemagne and his successors, having learned of it through the Northumbrian scholar Alcuin. It was this influence of the Royal Frankish court that popularized the usage and spread it east into German speaking territories. The Carolingian use of AD may well have had twin ideological reasons of breaking away from using the Byzantine era and defusing certain strains of apocalyptic thought. Just a note: While it is increasingly common to place AD after a date, by analogy to the use of BC, formal English usage adheres to the traditional practice of placing the abbreviation before the year, as in Latin (e.g., 100 BC, but AD 100). http://en.wikipedia.org/wiki/Anno_Domini