Compare “Date” field in Oracle [closed]

Question

I have 2 questions:

1. I want to compare a field whose data type is "Date" against a given date. The DB is oracle and being a mysql guy I'm finding it difficult to come up with simple queries.

The field("date_closed") stores date in UTC format (24-Aug-2011 18:55:11 for example) and I want to convert it to PST for comparison

I tried this query but it returns some extra rows in the data set(obviously):

select * from table1 where trunc(date_closed)=to_date('2011-08-24','yyyy-mm-dd')

How do I covert to PST format before comparison?

2.In the same query how do I compare "date_closed" against the current date?