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

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Sun Jan 28 02:12:11 UTC 2018

On 2018-01-27 11:13, Paul Eggert wrote:
> J William Piggott wrote:
>> why not get the offset directly from TZ/tzfile the
>> same way tzset does for tm_gmtoff
> Let me try to be clear about the question since I evidently didn't understand
> your previous email. When you write "get the offset directly from TZ/tzfile", I
> assume you don't mean that users are expected to write complex code that behaves
> like tzcode's localtime.c and that goes off and parses the TZ environment
> variable and/or reads files in tzfile format and get the offset directly from
> that string or data. Instead, I assume you are asking for an API that lets users
> easily determine the UTC offset of a timestamp.
> For tzcode, GNU/Linux, FreeBSD, etc., that API is already there: it's the
> tm_gmtoff member of struct tm. For POSIX there is no such API, so one must play
> the diff(LOCALTIME,GMTIME) trick.
> One could design a different API to do what tm_gmtoff does, an API that uses a
> function rather than a structure member, and implement this function by doing
> what tzset does and a little bit more. However, as far as I know, nobody has
> done that for C in any widely-used distribution, and there's been no need to do
> it because tm_gmtoff already handles the problems that the function would address.

NetBSD supports tzgetgmtoff(), tzgetname(), with tz and isdst parameters, since
~4.{2,3} according to ESR's doc.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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