The continuing use of AD and BC is not only factually wrong but also offensive to many who are not Christians.
What year is it? This most basic of historical questions yields no universal answer. For Orthodox Jews, counting from the putative creation of the universe, the October 2009 issue of History Today, where this article first appeared, was published Anno Mundi 5770. According to the Muslim lunar calendar, dating from Muhammad's Hijra (flight or emigration) from Mecca, it is now ah 1430. Persians, Mayans, Jains, even Freemasons, all have their own eras. But it is the Christian era, counting 'the years of the Lord' from the birth of Christ, that is now ubiquitous in business, politics and historical writing. In that system, it is 2009 - but should one say ad 2009 or, as is increasingly common among scholars, 2009 CE - 2009 of the 'Common Era'?
The Common Era retains a Christian reference point - the birth of Christ - but this may be regarded as a historical accident of globalisation. As former UN General Secretary Kofi Annan put it in a statement marking the turn of the millennium: The Christian calendar no longer belongs exclusively to Christians.' For some, these are fighting words: the Southern Baptist Convention resolved, also in 2000, to resist the 'revisionism' implicit in the CE/BCEsystem and to retain AD 'as a reminder to those in this secular age ... that history Is ultimately His Story'.
The AD/BC chronology is not so ancient as some proponents suppose; nor is the CE/BCE system so recent. For the first five centuries of their religion, Christians marked time according to local conventions, usually from the legendary foundation of Rome (753 BC), or from the Diocletian reforms (284 AD). In a sixth-century treatise on the calculation of Easter, Dionysius 'the Little' first proposed to count from the birth of Christ to avoid honouring the hated persecutor Diocletian. His idea was popularised in England by the Venerable Bede, who added the notion of counting backwards for dates 'Before Christ'. However, it only gained universal acceptance among Christians in the 15th century. Meanwhile, in 1615 Johannes Kepler used the phrase anno aerae nostrae vulgaris (in the year of our common era) in an astronomical table and 'Common Era' or its equivalents are known, if rare, in 18th-century works such as the Encyclopaedia Britannica of 1797.
Since the Christian and the secular chronologies yield identical dates (ad 2009 equals 2009 CE) why convert from one to the other? Isn't this an example of political correctness run wild, the Chronometrie equivalent of replacing 'Merry Christmas' with 'Happy Holidays'?
I don't think so. Consider, for example, the historical problems raised by using the AD/BC system to discuss a relatively uncontroversial fact the dating of the biblical Book of Daniel. Scholars agree that most of it was written in the early second century BC, during the reign of Antiochus Epiphanes, who outlawed Judaism and defiled the Temple with a golden image of himself (the miracles attending the rededication of the Temple give us the Jewish festival of Hanukkah).
Daniel is sacred to Christians and Jews; it is part of the Christian Old Testament and the Hebrew Bible. An impartial historian should not take sides on its interpretation within either religion. But to say that Daniel was written in a given century BC is to do so. BC means 'before Christ', and 'Christ' is English for the Greek Khristos or 'anointed one; a literal translation of Hebrew Messiah. Daniel owes its prominence in both Jewish and Christian thought to prophecies concerning the coming in glory of a 'son of man' (the Messiah) and his foundation of a 'holy kingdom of God'. The use of BC, however unintentionally, suggests that the prophesied Messiah arrived with Christ, whose birth initiated the kingdom of God on earth. Henceforth we have lived in the age of Christ's working in history: the years of Our Lord' - Anno Domini. The AD /BC notation presupposes, then, that the Christian interpretation of the Book of Daniel is the right one. In contrast, dating by 'Common Era' and 'Before Common Era' takes no side in such a discussion: it simply fixes an event in time.
Our temporal labels are saturated with religion. Weekdays commemorate Norse and Roman gods (compare English Thursday -'Thor's Day'- with French jeudi or 'Jove's Day'). Weekends derive from the Jewish Sabbath. Even our sexagesimal minutes and seconds come, ultimately, from the base-60 calculations of Babylonian astrology. If we can have pagan weeks, months and seconds, why not Christian years? Is not the CE/ BCE notation another attack, by secular culture, on Christianity?
Again, I don't think so. Weekdays and months are part of everyday speech and practice - attempts to change them, such as the Puritan campaign to number the days and thus avoid pagan idolatry, is an example of social engineering. Chronological notation, on the other hand, is part of the technical vocabulary of the historical disciplines. If we want our history to be religiously neutral, if we are practising pluralistic or non-religious scholarship, then we should acknowledge that time belongs to everyone, not just to Christians. Only then will our historical practice be truly common.
A final argument: the AD/BC system is factually wrong. Due to a misreading of the dates for Augustus Caesar, Dionysius the Little miscalibrated 1 ad. Christ was born, according to the best estimates, around 4 BC - an unproblematic statement in common-era notation, but one that would raise thorny theological issues should we say that Christ was born four years 'before Christ'.