When was the current BC/AD calendar system introduced and how were years measured before its adoption? | Notes and Queries (2024)

When was the current BC/AD calendar system introduced and how were years measured before its adoption?

A Chapman, Cheshunt, UK

• I believe this was introduced with the Gregorian calendar by Pope Gregory XIII in the 16th century. Prior to that, the year was not standardised throughout the world. The Romans dated everything from the (semi-mythical) date of the foundation of the city, 753 BC. The Japanese dated things according to the year of the Emperor's reign (and still do for some internal purposes). Muslims and Jews have their own traditional calendars.

  J Rhoades, Maidstone

• The BC/AD system was invented by a monk named Dionysius Exiguus who was trying to establish a Christian chronology; before his time one had to use some system more or less tainted with paganism, such as the AUC system (from Rome's foundation) or consular dating ("the year when X and Y were [Roman] consuls" - by the sixth century of our era there had been more than a thousand pairs of consuls, which had to be memorized in order). Dionysius calculated that the year in which he worked was the 533rd since the birth of Christ, so he designated it AD 533 (or AD DXXXIII). It took some time for Dionysius' scheme to catch on. Bede is the first writer other than Dionysius himself to use it; he dated one of his works AD 704. Still, it wasn't used universally - the Spanish used an era based on 38 BC well up into mediaeval times, while the Byzantines dated from 5508 BC. It was pretty well established in Western Europe (other than Spain) by AD 1000.

  B Kenney, Gerogetown, Indiana USA

• I invented the BC/AD calender. Before i invented it i measured years according to the length of my legs. Therefore as i grew older the years got longer. As this could be quite confusing, especially during growth spurts, i knocked up the BC/AD calender.

  Hugh J Cox, Glasgow Scotland

• Dionysius Exiguus & his successors, not having mastered the Oriental concept of zero, neglected to provide for one between BC & AD, which is why one cannot calculate the difference between BC & AD by summing the dates.

  Jeffry Larson, Hamden, CT USA