Error in date_trunc function?

Compare TZ part of date_func function output with param 'month' and other.
Is it error?

netquote=> select date_trunc('century', now());
       date_trunc
------------------------
 2000-01-01 00:00:00+03
(1 row)

netquote=> select date_trunc('year', now());
       date_trunc
------------------------
 2001-01-01 00:00:00+03
(1 row)

netquote=> select date_trunc('month', now());
       date_trunc
------------------------
 2001-10-01 00:00:00+04
(1 row)

netquote=> select date_trunc('day', now());
       date_trunc
------------------------
 2001-10-31 00:00:00+03
(1 row)

netquote=> select date_trunc('hour', now());
       date_trunc
------------------------
 2001-10-31 18:00:00+03
(1 row)

netquote=> select date_trunc('minute', now());
       date_trunc
------------------------
 2001-10-31 18:12:00+03
(1 row)

netquote=> select date_trunc('second', now());
       date_trunc
------------------------
 2001-10-31 18:12:24+03
(1 row)

--
Marat Khairullin        8->     mailto:xmm@rambler.ru
                                   Marat.Khairullin@f92.n5049.z2.fidonet.org