Getting the week of a date

test=# select date_trunc('month',current_date + ('5 month')::INTERVAL);
     date_trunc
---------------------
 2004-07-01 00:00:00
(1 row)

 

test=# select date_trunc('week',current_date + ('5 month')::INTERVAL);
ERROR:  TIMESTAMP units 'week' not supported
test=#

 

Any idea on how to find the 3 rd Wednesday of any given month.

 

Thanks

Kumar