The year 0 AD

Chris Carrier 72157.3334 at CompuServe.COM
Fri Jan 3 04:19:17 UTC 1997

"Markus G. Kuhn" > INTERNET:kuhn at
>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.

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