Re: Why data of timestamptz does not store value of timezone passed to it?

From: "ktm(at)rice(dot)edu" <ktm(at)rice(dot)edu>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Kevin Grittner <kgrittn(at)ymail(dot)com>, Steve Crawford <scrawford(at)pinpointresearch(dot)com>, rohtodeveloper <rohtodeveloper(at)outlook(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Why data of timestamptz does not store value of timezone passed to it?
Date: 2014-08-28 19:46:16
Message-ID: 20140828194616.GD11672@aart.rice.edu
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On Thu, Aug 28, 2014 at 03:33:56PM -0400, Bruce Momjian wrote:
> On Thu, Aug 28, 2014 at 11:26:53AM -0700, Kevin Grittner wrote:
> > Steve Crawford <scrawford(at)pinpointresearch(dot)com> wrote:
> >
> > > I have always considered "timestamp with time zone" to be a bad
> > > description of that data type but it appears to be a carryover
> > > from the specs. It is really a "point in time"
> >
> > I agree.  While what timestamptz implements is a very useful data
> > type, I think it was a very unfortunate decision to implement that
> > for the standard type name, instead of something more consistent
> > with the spec.  It seems very unlikely to change, though, because
> > so much existing production code would break.  :-(
> >
> > Understandably, people do tend to expect that saving something into
> > a column defined as TIMESTAMP WITH TIME ZONE will save a time zone
> > with the timestamp, and in PostgreSQL it does not.
>
> So the standard requires storing of original timezone in the data type?
> I was not aware of that.
>

I do not have a copy of the SQL 92 spec, but several references to the
spec mention that it defined the "time zone" as a format "SHH:MM" where
S represents the sign (+ or -), which seems to be what PostgreSQL uses.

Regards,
Ken

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