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From: mark@drd.com (Mark Lawrence)
Newsgroups: comp.databases,comp.software-eng,comp.infosystems
Subject: Re: Time Zones HELP!
Message-ID: <1991Apr9.132029.8367@drd.com>
Date: 9 Apr 91 13:20:29 GMT
References: <1991Apr5.234855.14441@odin.corp.sgi.com> <1991Apr6.021724.6578@sctc.com> <1991Apr6.182727.16147@ingres.Ingres.COM>
Organization: DRD Corporation
Lines: 34

In article <1991Apr6.182727.16147@ingres.Ingres.COM> jas@Ingres.COM (Jim Shankland) writes:
>Think of time zone information as a display format for an absolute
>time, somewhat analogous to a floating point display format.  The
>database itself must store absolute time (in practice, Greenwich Mean
>Time), while the client chooses a display format (i.e., timezone)
>in which to display that time, probably on a per-session basis.
>(Unless you really believe that noon in San Francisco comes before
>1 p.m. in New York -- which would be a curious model of time.)

Excellent suggestion.

>Arthur David Olson of NIH (I think) has written a timezone library in
>C that does as much of this stuff as possible.  It includes tables
>encoding the whims of dozens of state and national legislatures.
>You should be able to pick this up from your comp.sources.unix
>archives, or FTP it from somewhere.  Ask around.

I'm using it now (in fact) to retrofit better handling of time/date into
our application.  Mike Wescott at NCR (thanks Mike!) gave me the pointer
I needed to find it.  He wrote:

> Look at getdate(3) which comes as a part of the News sources.  It does
> the picking and the conversion to standard unix format.
> 
> Also look at the routines that came as part of the v18i111-7 posting in
> comp.sources.unix: "Table-driven ctime/time/localtime/date package"
> for ideas.  There is a struct tm to time_t conversion routine in there,
> using a binary search to do the conversion.

found mine at uunet v18 archives.  You can find yours at finer anon ftp
sites everywhere.
-- 
mark@drd.com
mark@jnoc.go.jp