BUG #6001: date_trunc is not timezone aware

The following bug has been logged online:

Bug reference:      6001
Logged by:          Marek Nos
Email address:      marek.nos@centrum.cz
PostgreSQL version: 9.0
Operating system:   Windows 7
Description:        date_trunc is not timezone aware
Details:

and other like extract() as well

SELECT date_trunc('day', '2011-05-02 02:00:00+05'::timestamptz)

I would expect result as
'2011-05-02 00:00:00+05'
but
'2011-05-01 00:00:00+02' is given (pre conversion to server timezone is done
first)