Where does the AD/BC dating convention come from?

I was already on record as expressing scepticism about Neil deGrasse Tyson’s forthcoming Cosmos television series, as I view his knowledge of the history of science as at least as bad if not worse than Carl Sagan’s was and that was pretty terrible. Yesterday evening my Twitter stream was full of people wondering what I would have thought of N dG T’s elevation of Giordano Bruno to the status of a great scientific thinker. Fortunately I can’t view Cosmos here in Germany and so I was spared this particular piece of history of science inanity. However I came across another wonderful example of N dG T’s fantasy version of the history of science today.

Massimo Pigliucci’s Rationally Speaking has a new podcast interview, Neil deGrasse Tyson on Why He Doesn’t Call Himself an Atheist. Tyson rejects the label atheist because of the expectations that radical atheists place on him, an attitude that I can more than sympathise with. The particular trigger for this discussion was Tyson being volubly criticised for using the expression god speed in a video, which he quite rightly regards as being an imposition. In the course of the discussion Tyson then goes on to list other Christian things that he likes, uses, accepts despite not believing in the Christian God. Again I have no argument with him in this. However he then let off a minor tirade about the calendar and those who reject the use of AD/BC.

Tyson’s argument was roughly as follows, The Gregorian Calendar is a great invention and should be respected. It was a Christian invention, created by Jesuit scientist. Accept it! (A paraphrase not a direct quote) This brief outburst contains a whole series of historical errors that are unfortunately typical for Tyson.

First off his main bone of contention the origins of the AD/BC dating system has nothing to do with Gregorian Calendar. The use of Anno Domini goes back to Dionysius Exiguus  (Dennis the Short) in the sixth century CE in his attempt to produce an accurate system to determine the date of Easter. He introduced it to replace the use of the era of Diocletian used in the Alexandrian method of calculating Easter, because Diocletian was notorious for having persecuted the Christians. Dionysius’ system found very little resonance until the Venerable Bede used it in the eight century CE in his Ecclesiastical History of the English People. Bede’s popularity as a historian and teacher led to the gradual acceptance of the AD convention. BC created in analogy to the AD convention didn’t come into common usage until the late seventeenth century CE. There is a certain irony in the fact that Dionysius miscalculated the birth of Christ who was most probably born sometime between six and four BCE. Whatever, the AD/BC dating convention has nothing to do with the Gregorian Calendar, although this did take it over.

Tyson’s little outburst however contains more historical errors. The Gregorian Calendar is indeed a Christian invention but it was not created by Jesuit scientists. First off to refer to anybody who existed before 1834 as a scientist is a historical anachronism to be avoided if at all possible. Personally I’m coming to the conclusion that the word scientist should be generally avoided, as it’s a highly ambiguous word, but that is the subject for another post. The people who created the Gregorian Calendar should be referred to as astronomers. Calendar creation and calculation has been the task of astronomers since the early years of antiquity.

Unfortunately for our intrepid science communicator the Gregorian Calendar was not created by the Jesuits. The original scheme for the calendar was worked out by Aloysius Lilius (vernacular either Luigi Lilio, or Luigi Giglio) who was a physician and astronomer from Calabria in Italy. Lillius was not a cleric of any sort let alone a Jesuit. His scheme was examined, contemplated and finally recommended by a committee that met irregularly over a period of more than ten years. The exact composition of this committee is not known, as it varied over the years, but nine members signed the final recommendation to the Pope of whom only one, the least significant member Christoph Clavius, was a Jesuit. Following the introduction of the calendar by the Catholic Church Clavius, at the request of the Pope, took over the defence of the new system of time measurement against its many critics, writing six books on the subject over the next thirty odd years, thus becoming closely associated with the calendar although he did not create it.

These are all facts that are easily accessible to anybody with use of a good library or who knows their way around the Internet (hint, hint Wikipedia!) and there is absolutely no excuse for Tyson to spout his fully incorrect version of history, which will unfortunately be accepted as gospel by his army of worshipers.

Addendum: Both the Jewish and the Islamic calendars are older than the Gregorian calendar so why should these two non Christian peoples accept the AD/BC dating convention? There are other older calendars in use in India, China, Persia, same argument. Also the Gregorian calendar is only a slightly modified version of the Julian calendar, which was distinctly non Christian and it was nothing more or less than the Egyptian solar calendar in use since about four thousand BCE, again anything but Christian.