On Jan 19, 2011, at 2:47 AM, Edward C. Zimmermann wrote:

> Tossing a wacky idea into the ring...
> Why not read the semantics for T as time since 0..
> 2011-01-17 is day precision
> 2011-01-17T01   is hour precision and means 1 AM
> 2011-01-17T01:02 is minute precision and means 1:02 AM
> This all agreed..  with this reading of T we get the T:24:00 and
> T12:60 paradigm extended to arbitary hours, minutes..
> 2011-01-17T25   would be hour precision and 1 AM on the 18th
> basically I am thinking of allowing for simple math... this could
> be interesting for dumb clients.

It depends, I guess, on whether you are seeking to
define a format for user input or for interchange among
parties.  It's often quite useful to accept a lot of forms
in user input that one does not want in a database or
document to be stored and interchanged.

Users may well type "19.01.2011" or "1/19/2011" or
"18 Jan 2011" or "on the 19th of this month", all meaning
the same thing.  But in metadata (as opposed to the 
transcription of historical or legal documents), is there 
an important goal to be achieved by preserving the differences 
among those forms, given that (by hypothesis) they all 
mean the same thing?

* C. M. Sperberg-McQueen, Black Mesa Technologies LLC