Time Zone File format - When does tzh_ttisgmtcnt or tzh_ttisstdcnt differ from tzh_typecnt, and how, and why?

[Jonathan Leffler]

On Dec 10, 2007 6:54 AM, Olson, Arthur David (NIH/NCI) [E] <
olsona at dc37a.nci.nih.gov> wrote:

> This is indeed historical; the tzh_tisgmtcnt and tzh_ttisstdcnt header
> fields (and associated variables) were introduced in 1995 to allow European
> time zones to be used as time zone templates, and the software had to be set
> up to handle older files from which the information was absent (and in which
> the header fields were zero).
>

Thanks for confirmation of this.
Should I submit a patch to tzfile.5 to document this?


> From: Jonathan Leffler [mailto:jonathan.leffler at gmail.com]
> Sent: Monday, December 10, 2007 1:20
>
> In tzfile.5.txt, it says:
>
> tzh_ttisgmtcnt
>  The number of UTC/local indicators stored in the file.
>
> tzh_ttisstdcnt
>  The number of standard/wall indicators stored in the file.
> ...
> tzh_typecnt
>  The number of "local time types" for which data is stored in the file
> (must not be zero).
>
> Empirically, in the tzdata2007h and tzdataj data sets, the values of
> tzh_ttisgmtcnt, tzh_ttisstdcnt and tzh_typecnt are always identical.
>
> Under what circumstances are there any differences in the three values?
> [...]
> If the answer is "there isn't any difference any more, but historically,
> there was a transition period when they weren't all present and the stdcnt
> and gmtcnt were sometimes zero back then", then I can live with that as a
> satisfactory enough explanation.
>


-- 
Jonathan Leffler <jonathan.leffler at gmail.com>  #include <disclaimer.h>
Guardian of DBD::Informix - v2007.0914 - http://dbi.perl.org
"Blessed are we who can laugh at ourselves, for we shall never cease to be
amused."
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