Query help

[novice <user.postgresql@xxxxxxxxx>]

Hi,
I have a table

select id, config_id, start_day, end_day, start_time, end_time from config;

 id  | config_id | start_day | end_day | start_time | end_time
-----+-----------+-----------+---------+------------+----------
   1 |       101 | Mon       | Sun     | 08:30:00   | 18:00:00
   2 |       101 | Mon       | Sun     | 18:00:00   | 22:00:00
   3 |       555 | Mon       | Fri     | 08:30:00   | 16:00:00



I'd like to write a query to generate the following... is it possible at all?

 config_id | day       | start_time | end_time
-----------+-----------+---------+-------------
       101 | Mon       | 08:30:00   | 18:00:00
       101 | Mon       | 18:00:00   | 22:00:00
       101 | Tue       | 08:30:00   | 18:00:00
       101 | Tue       | 18:00:00   | 22:00:00
       101 | Wed       | 08:30:00   | 18:00:00
       101 | Wed       | 18:00:00   | 22:00:00
       101 | Thu       | 08:30:00   | 18:00:00
       101 | Thu       | 18:00:00   | 22:00:00
       101 | Fri       | 08:30:00   | 18:00:00
       101 | Fri       | 18:00:00   | 22:00:00
       101 | Sat       | 08:30:00   | 18:00:00
       101 | Sat       | 18:00:00   | 22:00:00
       101 | Sun       | 08:30:00   | 18:00:00
       101 | Sun       | 18:00:00   | 22:00:00
       555 | Mon       | 08:30:00   | 18:00:00
       555 | Tue       | 08:30:00   | 18:00:00
       555 | Wed       | 08:30:00   | 18:00:00
       555 | Thu       | 08:30:00   | 18:00:00
       555 | Fri       | 08:30:00   | 18:00:00

Thanks