to_char("HH12") with intervals

bruce wrote:
> bruce wrote:
> > Dave Page wrote:
> > > This was posted as a documentation comment:
> > >
> > > to_char(interval '0d 0h 12m 44s', 'DD HH MI SS');
> > > with HH and HH12 will return 12 instead of 0.
> > >
> > > Testing on 8.4.1, it does seem to be the case that you get "00 12 12
> > > 44". Seems bogus to me, but am I and the OP missing something?
> >
> > Fixed with the attached patch. I think HH and HH24 should be the same
> > for intervals. It is hard to explain why zero hours should show as
> > '12' for intervals.
>
> Oops, I needed a second patch to fix hours > 12 for intervals. Patch
> attached and applied. It will now report the full hours of the
> interval.

We currently have this in our documentation:

<function>to_char(interval)</function> formats <literal>HH</> and
<literal>HH12</> as hours in a single day, while <literal>HH24</>
can output hours exceeding a single day, e.g., &gt;24.

This seems pretty confusing because HH/HH12 formats as hours in a single
1/2 day, 12 hours, and it really does wall-clock time, zero hours is 12,
and for intervals it does the right thing now and prints the interval
hours.

We also have these range definitions:

<row>
<entry><literal>HH12</literal></entry>
<entry>hour of day (01-12)</entry>
</row>
<row>
<entry><literal>HH24</literal></entry>
<entry>hour of day (00-23)</entry>
</row>

HH24 could always be > 24 for intervals, and now HH12 can too for
intervals.

What should be changed here?

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
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