The meaning and use of BC and AD.
These are simply abbreviations, BC for Before Christ, and AD [the second is Latin], 'Anno Domini' which translated into English means, "The year of our Lord Jesus".
This is counting from when Jesus was born, but the first serious calendar reckoning was done about 450 years after Jesus was born, and the calendars were imprecise. Fortunately the reckoning was not too far off.
It is generally believed that Jesus was born in the year 2 BC going by our current calendar. Some opinions have suggested 4 - 6 BC but careful calculations backwards from the date of John's baptism gives us 2 BC as the most accurate calculation. John the Baptist began his ministry according to Luke 3:1-3 in the 15th year of Tiberius' reign. Tiberius succeeded Augustus in the empire, and began his “sole” reign Aug. 19th, AD 14. John was then thirty years old, and shortly after this Jesus came to be baptized by John, who was six months older than Jesus.
When using these terms, it is proper to place them closest to the year "0" in the calendar.
So you would write, 17 BC, but for dates after the birth of Jesus, the term precedes the number, AD 37.
A date spanning the timeline - before and after the birth of Jesus, would read as: 400 BC- AD 100.
You may also see BCE meaning 'Before Common Era', which is another way of saying "Before Christ", and CE 'Common Era', which is the same as AD = 'The year of our Lord Jesus'.
These latter abreviations are used by those who wish to avoid referring to Jesus, whose birth divided history into BC and AD.
© 2013 Jim Cole-Rous