[LEAPSECS] ISO 8601 Z designator improper before 1972?

[Rob Seaman]

Hi,

There are requirements here (unstated as usual :-) from both  
historical and future usage.  It is important to tie them together  
properly.  This is particularly true if entertaining the possibility  
of sundering UTC from UT.

Poul-Henning Kamp wrote:


> "Zulu Time" is much older than 1972 and the 'Z' designator goes  

> waaay back.



 From this point of view, Z means simply "Universal Time".  That is,  
there was an adoption by ISO 8601 of a prior meaning.  ITU must  
clarify such contingent issues if UTC is to be amputated from the  
broader meaning of Universal Time.  (Or ITU might want to invest some  
brain cells in considering what it will do regarding the mess it will  
leave behind :-)

Gerard Ashton wrote:


> Similarly, within ISO 8601, "Z" designates "UTC" and any meaning it  

> may have had for most of the 20th century outside that standard is  

> irrelevant.


I don't know if I agree with the latter part of the sentence since Z  
retains usage outside of ISO 8601, but in cases where some system  
architect has decried that some data structure adheres to ISO 8601,  
then that data structure should indeed be interpreted very  
pedantically with reference to the standard.

There is an interesting issue parsing free format strings since an ISO  
8601 compliant substring might be preceded by some sequence of  
characters (perhaps not even ASCII) that are non-compliant, or indeed  
it might be followed by some sequence of characters - such as a 'Z' -  
with an ambiguous meaning, e.g.:

	<a sequence of chars>2009-02-09T19:37:57<Zanother sequence of chars>

Does the Z belong to the ISO substring?  There are other similar edge  
cases - for instance, are the date and time tied together atomically  
at all?

On the other hand, if you state that a field must represent only ISO  
8601 compliant values, then the meaning of the Z is controlled.

Rob