PostgreSQL JDBC - Java's set of timezone names (was: Re: Timestamp Conversion Woes Redux)

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Java's set of timezone names (was: Re: Timestamp Conversion Woes Redux)

Vadim Nasardinov

2005-07-20, 1:23 pm

On Wednesday 20 July 2005 13:41, Tom Lane wrote:
> Hmm ... does Java have a standard set of timezone names? If so,
> does it bear any resemblance to the zic database names?

I'm not sure how Roedy Green knows this, but this is what he has to
say on the subject in his Java Glossary:

http://www.mindprod.com/jgloss/timezone.html

The names for timezones used in Java comes from a list maintained
at NIH by Arthur David Olson. For reasons only he understands,
Pacific Standard Time is called America/Los_Angeles.

As far as I can tell, Olson's timezone data can be found here:
ftp://elsie.nci.nih.gov/pub/

Sun's JDK puts timezone data in $JAVA_HOME/jre/lib/zi/

Sun's JDK's timezone info seems fairly different from what, say,
Fedora Core distributes in its tzdata RPM:

| $ find /usr/share/zoneinfo/ -type f -printf '%P\n' | sort > /tmp/linux-tzdata.txt
| $ find /usr/local/j2sdk1.4.2_08/jre/lib/zi -type f -printf '%P\n' | sort > /tmp/java-tzdata.txt
| $ diff /tmp/linux-tzdata.txt /tmp/java-tzdata.txt | wc -l
| 1309

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Tom Lane

2005-07-20, 1:23 pm

Vadim Nasardinov <vadimn@redhat.com> writes:
> I'm not sure how Roedy Green knows this, but this is what he has to
> say on the subject in his Java Glossary:

> http://www.mindprod.com/jgloss/timezone.html

> The names for timezones used in Java comes from a list maintained
> at NIH by Arthur David Olson. For reasons only he understands,
> Pacific Standard Time is called America/Los_Angeles.

> As far as I can tell, Olson's timezone data can be found here:
> ftp://elsie.nci.nih.gov/pub/

Hmm ... that is the zic distribution, so if this information is accurate
there should be a pretty exact match in the sets of names ... which it
sounds like there is not.

> Sun's JDK's timezone info seems fairly different from what, say,
> Fedora Core distributes in its tzdata RPM:

Fedora's info also comes from zic.

regards, tom lane

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Dave Cramer

2005-07-20, 8:24 pm

On 20-Jul-05, at 2:29 PM, Tom Lane wrote:

> Vadim Nasardinov <vadimn@redhat.com> writes:
>
>
>
>
>
>
>
>
> Hmm ... that is the zic distribution, so if this information is
> accurate
> there should be a pretty exact match in the sets of names ... which it
> sounds like there is not.

On my Mac my java timezone was set to Canada/Montreal which was
broken (did not use DST ) and the server certainly
doesn't understand it.

The server on the same machine had the timezone set to Canada/Eastern
which java understands and I hacked the driver code to use the server
timezone. This seems to work. There's still a fair bit of ambiguity
as to whether java will do the right thing with the server supplied
time zones though?

It appears that timestamp, date, calendar in java are all terribly
implemented. I'm starting to see more and more why other DBMS
implemented their own setTimestamptz.

>
>
>
> Fedora's info also comes from zic.
>
> regards, tom lane
>
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>
>

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