[LEAPSECS] Leap second mess at NASA

Zefram zefram at fysh.org
Thu Jun 2 09:52:35 EDT 2011

Daniel R. Tobias wrote:

>"Current CDF_Epoch time scheme is nominally continuous Gregorian time

>from 0AD"... unfortunately for them, there wasn't actually any such

>year as "0 AD", since the real years went straight from 1 BC to AD 1.

"AD 0" is a perfectly meaningful label. It refers to the year before AD
1; that year is also known as 1 BC. Likewise, AD -1 is 2 BC, and so on.
This kind of year numbering is common in astronomy, and was written into
the latest version of ISO 8601. The use of AD year numbers below 1 is,
of course, contrary to convention in less technical contexts.


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