>-----Original Message-----
>From: Antoine Leca [mailto:Antoine.Leca@renault.fr] 
>Sent: Thursday, April 01, 1999 4:51 AM
>To: Lee Geoff
>Cc: tz@elsie.nci.nih.gov
>Subject: Re: storing timestamp data
>
>
>Lee Geoff wrote:
>> 
>> I'm interested in storing date/time data in Ingres
>> databases which are running on Unix servers. We are 
>recording timed events
>> on Unix servers as well as Windows 3.1 and NT PCs.  I have 
>had problems with
>> the apparent miss-handling of data when viewed before or after a DST
>> transition.
>
>We had this kind of problems when setting up a Internet 
>standard for exchanging
>calendars, agendas and schedules (it ends up in RFC2245, if you mind).
>
>The net result was: either use UTC, or local time + offset from UTC.
>Do not use local time without UTC offset, as no reliable method can be
>set up to correctly retrieve the exact point of time 
>afterwards (as you may
>have experienced).
>
>Using UTC times is native on Unix and NT (AFAIK), so this is 
>the basic choice
>there.  The problem comes with Windows non-NT PCs, since they 
>run local clocks.
>IMHO, and to be consistent with the above, no data that are 
>not tagged with
>the (best approximation of) UTC offset should leave the PC.
>
>Traditional way of finding the best approximation are (in order):
> - search for an (up to date) Olson's package to interpret the 
>information,
>  perhaps by searching $(DJDIR)/zoneinfo/localtime in addition to 
>  $(TZDIR)/localtime
> - if running on Windows 95/98, search the information in the registry
> - setting a mechanism dedicated to it (but it will end with one more
>  mechanism, which tends to upset users)
> - ask the TZ environment variable
> - search the information on related softwares that may be 
>present on the PCs
>  (examples are mailing systems, e.g. Notes, and IP 
>connectivity packages)
>
>Do not use:
> - tzset and timezone, as it defaults to PST8PDT or EST5EDT on 
>most compilers,
>  without being reliably accurate on most workstations by lack of TZ
> - if your users are not Americans, do not rely on US-based 
>rules; they are
>  almost correct for Europeans (except that for example, this 
>week, my UTC
>  offset is wrong because my mail software is brocken on this 
>respect...)
>
>
>Hope it helps,
>
>Antoine
>
>