Update date format in SQL developer

Question

I need to convert date format in SQL developer , it's varchar2 format now
The current format is yyyy/mm/dd-hh:mm:ss:sss and I need to convert it to yyyy-mm-dd hh:mm:ss CST
I don't really know SQL but did some research and found that I can use instr to find the string and replace it, however, no matter what I try,there is always something off :(
Could anyone here help me with it? thanks in advance.

Answer 1

create table xo_custom_date_format (mydateAsChar varchar2(100));
table XO_CUSTOM_DATE_FORMAT created.
insert into xo_custom_date_format
values ('2012/03/23-09:52:24:123')
+1 rows inserted.+
select mydateasChar from xo_custom_date_format
mydateaschar
+2012/03/23-09:52:24:123+
select to_timestamp(mydateaschar, 'YYYY/MM/DD-HH24:MI:SS:FF3') mydateAsTimestamp from xo_custom_date_format
-- We must convert to timestamp data type, rather than date data type as you have fractions of seconds
mydateAsTimestamp
+23-MAR-12 09:52:24.123000000 --<-- This will probably appear differently, depending on your database NLS_ settings (i.e. what country you are in)+
select to_char( to_timestamp(mydateaschar, 'YYYY/MM/DD-HH24:MI:SS:FF3') , 'YYYY-MM-DD HH24:MM:SS')||' CST' as myDateReformatted
from xo_custom_date_format
mydateReformatted
[phone]:03:24 CST+