Oracle timezone conversion

Question

I have a requirment in which the database server time is being changed to GMT but one of the database users needs to store its data in CST or CDT as the case may be depending on daylight savings .I am thinking of writing a function which returns depending on date value passed on to it whether it is CST or CDT (depending on the day of the year ) and thiS function would be called from a before insert trigger for the tables so that the date data being passed on GMT time is converted back to CST or CDT before storing and stored as such then .Is this the best approach ,does oracle have a system function for this ? NEW_TIME is the function that I am aware of for timezone conversion however it doesnt take into consideration if it is CST or CDT .Thanks

Answer 1

What is the datatype - date, timestamp, timestamp with timezone?
There are ways of converting the date which includes daylight savings time considerations;
SQL> select sessiontimezone from dual
SESSIONTIMEZONE
-08:00        
1 row selected.
SQL> create table t(ts timestamp)
Table created.
SQL> insert into t values(to_timestamp('01-jun-2007 12:00:00', 'dd-mon-yyyy hh24:mi:ss'))
1 row created.
SQL> insert into t values(to_timestamp('01-dec-2007 12:00:00', 'dd-mon-yyyy hh24:mi:ss'))
1 row created.
SQL> SELECT ts,
   ts AT TIME ZONE 'UTC' utz,
   ts AT TIME ZONE 'Canada/Central' ctz
FROM t
TS                         UTZ                               CTZ                             
2007-06-01 12:00:00,000000 2007-06-01 20:00:00,000000 +00:00 2007-06-01 15:00:00,000000 -05:00
2007-12-01 12:00:00,000000 2007-12-01 20:00:00,000000 +00:00 2007-12-01 14:00:00,000000 -06:00