Re: [HACKERS] timezone problem?

Tatsuo Ishii wrote:
> 
> > Thomas Lockhart <lockhart@alumni.caltech.edu> writes:
> > > HST is interpreted by Postgres as Hawaii Standard Time, which is on
> > > the other side of the date line from Japan. Planning a vacation
> > > Tatsuo?? :))
> 
> I wish I could do so:-) I hate the cold winter in Japan...
> 
> > Then there's still something wrong:
> >
> > > test=> select '1998-09-23 12:05:10 HST'::datetime;
> > > ------------------------------
> > >  Wed Sep 23 22:05:10 1998 JST
> >
> > 10 hours behind JST (= GMT+9, IIRC) is in the wrong ocean to be
> > Hawaii...
> 
> Right. HST is GMT-10, and JST - HST = 19 hours. So '1998-09-23
> 12:05:10 HST' shoud be 'Thu Sep 24 07:05:10 1998 JST', rather than 'Wed
> Sep 23 22:05:10 1998 JST'...
> 
> Looking into the zoneinfo files under /usr/share/zoneinfo, I found 'Japan'
> as a valid zone name (I could not find 'JST' too on my RH box).
> 
> test=> select '1998-09-23 12:05:10 HST'::datetime;
>            ?column?
> ------------------------------
>  Thu Sep 24 07:05:10 1998 JST   -- correct
> (1 row)
> 
> test=> set timezone to 'JST';
> SET VARIABLE
> test=> select '1998-09-23 12:05:10 HST'::datetime;
>            ?column?
> ------------------------------
>  Wed Sep 23 22:05:10 1998 JST   -- wrong. seems interpreted as GMT (UTC)
> (1 row)
> 
> test=> set timezone to 'Japan';
> SET VARIABLE
> test=> select '1998-09-23 12:05:10 HST'::datetime;
>            ?column?
> ------------------------------
>  Thu Sep 24 07:05:10 1998 JST   -- correct. but why showed as JST?
> (1 row)

That is typical when you use the long form of the time zone name such
as "Japan". You will also find a "US/Pacific" on your machine:

[root@golem zoneinfo]# setenv TZ US/Pacific
[root@golem zoneinfo]# date
Thu Jan 20 21:24:24 PST 2000

which is the same as PST8PDT.

In /usr/share/zoneinfo/US, the mysteries of the various states'
conventions are revealed:

[root@golem zoneinfo]# ls -1 US
Alaska
Aleutian
Arizona
Central
East-Indiana
Eastern
Hawaii
Indiana-Starke
Michigan
Mountain
Pacific
Samoa

where, as Vince pointed out, Indiana, Michigan, and Arizona seem to be
special cases within the usual three timezones.

> Seems something wrong with my RH 5.2. Note that FreeBSD does have the
> problem.

Sorry, FreeBSD also has the problem, or does not??
                   - Thomas

-- 
Thomas Lockhart                lockhart@alumni.caltech.edu
South Pasadena, California