BUG #7886: date_trunc(date) returning timestamptz instead of timestamp

The following bug has been logged on the website:

Bug reference:      7886
Logged by:          Nick Baxter
Email address:      nick.baxter@gmail.com
PostgreSQL version: 9.0.3
Operating system:   Linux 2.6.18
Description:        =


9.9.2. indicates that date_trunc can be called with a date value (which will
be cast to a timestamp). And regardless of the input, that the result will
be of type timestamp. When I call it with a date, I get a timestamp with
time zone instead, as indicated by the psql output.

# select date_trunc('month',date '2013-2-15');
       date_trunc
------------------------
 2013-02-01 00:00:00-06
(1 row)