FW: Australian Timezone issues.

Chris Bitmead chris.bitmead at bigfoot.com
Tue May 11 10:50:30 UTC 1999

Robert Elz wrote:

> You might want to ask them why they're bothering with time zone 
> names at all.

Well it appears that they are working around the problems that arguably
should fixed by the system timezone files. For example they recognise
"AEST" as Australian Eastern Standard Time and "CAST" as Central
Australian Standard Time..
>   | But there doesn't seem to be a portable way to find out the 
>   | string
>   | "Australia/Sydney" on your computer.
> No, nor can there be.   The very idea of the TZ variable is so 
> that users
> can define the zone in which they prefer time values to be 
> displayed.
> It makes no sense for the system to attempt to tell you what
> value you should use. 

Yes but there needs to be a default time zone for a machine. If the user
has set TZ, no problem you just go getenv(), but if you are relying on
the system default like 97% of people do, you can't find out what zone
to use.

>  If all you want is to use "local" time, then TZ ought not
> be being used at all (except in those brain damaged system V 
> implementations where that is the only way to tell the 
> libraries what zone should be used, in which case the default 
> value is supposed to be set in some system wide initialisation 
> a file).

"some file" are the key words here. You can't write portable code to
find out the user's zone unless they have explicitly set TZ which people
rarely do.

> No, 99% of the time the human should just use the system 
> defined local time, and not attempt to override it at all.   
> For the rest, then should use the
> location defined TZ value (Australia/Sydney and the like).  

If it's admitted that the abbreviation is of no value, then why not
abandon it and just report Australia/Sydney as the zone? The fundamental
point is that the data that comes _out_ of the system ("EST"), is
invalid when it is put back _in_. If the user sees "EST" come out of a
piece of software (Unix date, or a database), they expect it to mean the
same thing when they put it back in. Is that such an unreasonable
assumption for a person to make?

Chris Bitmead
mailto:chris.bitmead at bigfoot.com

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