[tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change

[Paul Eggert]

Robert Elz wrote:
>    From: Paul Eggert<eggert at cs.ucla.edu>
>    Date: Fri, 26 Jan 2018 07:39:30 -0800
>    Subject: Re: [tz] OpenJDK/CLDR/ICU/Joda issues with Ireland change
> 
>    | Unfortunately tm_gmtoff is not standardized by C or POSIX, perhaps
>    | because standardizers mistakenly thought that strftime %z was enough.
> 
> No, it would have been because tm_gmtoff isn't available everywhere
> (and most particularly, wasn't available on the main reference system
> from which most of POSIX was copied.)

strftime %z wasn't available on the main reference system either, nor was it 
universally supported, and yet it was added to the C standard. Since tm_gmtoff 
and tm_zone are supported by GNU/Linux and by the BSDs, they're pretty much 
everywhere but in traditional APIs such as AIX and Solaris. The main objecting 
to adding them there, as I understand it, is that it requires changing the size 
of 'struct tm' and that this is more of hassle than adding a conversion spec to 
strftime. Unfortunately strftime "%z" doesn't suffice to determine the full UT 
offset.

I used to be a regular contributor to POSIX standardization but dropped out due 
to lack of time. If there is a way I could contribute in the timestamp area (but 
not get deluged by other topics) I'd could resume.