Re: BUG #18445: date_part / extract range for hours do not match documentation

PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> In https://www.postgresql.org/docs/8.1/functions-datetime.html

It would be a good idea to look at versions of the documentation
that aren't so many years obsolete. 8.1 has been EOL since 2010.

> We say that EXTRACT() should return a number between 0-23 for hours

What it says now is

The hour field (0-23 in timestamps, unrestricted in intervals)

(This wording is currently only visible at
https://www.postgresql.org/docs/devel/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT
but it will propagate into the website's copies of still-maintained
branches at our next quarterly updates.)

> The function seems to also return 24 in some cases eg:
> SELECT date_part('hour', cast('24:00:00.00' as time))::int
> Could we update the documentation or modify the function so that it wraps 24
> back to 0 hours?

That edge case for type "time" is deliberate; see the definition
of that type in table 8.9 here:

https://www.postgresql.org/docs/devel/datatype-datetime.html

I don't really feel a need to clutter the documentation for EXTRACT()
still more by mentioning it there, especially since the current
wording is not wrong, just silent about that detail.

regards, tom lane