Awhile back, the BBC website History Extra had a post that included this tidbit:
AD 0… the date that never was
The AD years of the Christian calendar are counted from the year of Jesus Christ’s birth, and, as the number zero was then unknown to the west, Dionysius began his new Christian era as AD 1, not AD 0. …
This evoked the ire of the noted historian Thony Christie. In a post Something is Wrong on the Internet, he explained:
Diagonal Argument 