A question about timezone

Hello,

Sorry if I have posted this to the wrong mailing list. Its my first post.

I have a problem that I hope someone can help me with.

I have inherited a postgresql DB which has a table containing a day of the
week, a time and a time zone. I need to translate all these times into UCT
but I need to keep track of which day of the week the new time relates to.

e.g. this 2 timestamps go to different days

one=# select '2010-12-09 22:00:00' at time zone 'MSK'
one-# ;
timezone
---------------------
2010-12-10 01:00:00
(1 row)

one=# select '2010-12-09 02:00:00' at time zone 'PST';
timezone
---------------------
2010-12-08 18:00:00
(1 row)

how can I do this using only dow and time?

Thank you.