The year 0 AD

[Chris Carrier]

"Markus G. Kuhn" > INTERNET:kuhn at cs.purdue.edu
 
>ISO 8601 provides no way to represent years before the year 0000, or
>after the year 9999.  This makes it difficult to represent timestamps
>in some historical applications.  To fix this, you might extend the
>syntax for date-fullyear to:
 
date-fullyear = ["-"] 4*DIGIT
 
>where the years are numbered ..., -0002, -0001, 0000, 0001, 0002, ....
>(Note that unlike the traditional Julian calendar, there is a year 0
>in the modern Gregorian calendar.)
 
WRONG!  Negative year numbers are not part of the Gregorian calendar.
 
There are two ways to number years before 1 AD, astronomical and historical.
 
In historical dating, the year 1 AD is preceded by 1 BC, as there was no
concept of 0 in Western civilization when Exigius set up the Anno Domini year
count in AD 532.
 
In astronomical dating, there is no BC: everything is AD, the year 1 AD is
preceded by the year 0 AD, which is preceded by -1 AD, preceded by -2, etc...
 
Here's a way to remember it: Julius Caesar was assassinated on 15 March 44 BC,
historical dating, and -43 March 15, astronomical dating.