On 1/11/2011 1:13 PM, C. M. Sperberg-McQueen wrote (in part):
>
> 7 The year zero
>
> Entry 110 reads in part
>
>     BC has no year zero, In the BC system the year before year 1 is 1
>     BC. Thus '-0999' means "1000 BC".
>
> By "BC" and "the BC system" I think you must mean "the Gregorian
> calendar".  The absence of a year zero applies not just to the time
> before the era, but also after.
>
>

The Gregorian calendar did not create the year numbering system, it 
adopted an existing system. I don't read Latin, so am unable to state 
for certain, but I don't believe the defining documents for the 
Gregorian calendar requires the use of the year numbering system devised 
by Dionysius Exiguus, together with the system for naming years before 
AD 1 which was devised by Bede.

Gerard Ashton