Timezone calculation question

Seems I've missed something important about time zones. On my server
i've got local timezone 'W-SU' (Moscow time):

=> show timezone;
TimeZone
----------
W-SU

=> select now();
now
-------------------------------
2009-03-24 13:23:39.655057+03

Till now all seems ok. Than i'm trying to figure out local time at near
region:

=> select now() at time zone 'UTC+4';
timezone
----------------------------
2009-03-24 06:28:30.383373

select now() at time zone 'UTC+3';
timezone
----------------------------
2009-03-24 07:24:11.011075

Seems like zone offset been added twice...
Server 8.3.5, OS FreeBSD 7.0-RELEASE

Which way should i get correct local time, when i've got timestamp with
timezone and name of the target timezone?

Thanks beforehand
--
MRJ