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