Compare the timestamp value between before and after 'alter session set time_zone'
SQL> SQL> create table t 2 (c1 timestamp with time zone, 3 c2 timestamp with local time zone) 4 / Table created. SQL> SQL> insert into t (c1,c2)values( current_timestamp, current_timestamp ); 1 row created. SQL> SQL> select * from t; C1 --------------------------------------------------------------------------- C2 --------------------------------------------------------------------------- 16-JUN-08 05.01.27.439000 PM -08:00 16-JUN-08 05.01.27.439000 PM 1 row selected. SQL> SQL> alter session set time_zone = '-08:00'; Session altered. SQL> SQL> select * from t; C1 --------------------------------------------------------------------------- C2 --------------------------------------------------------------------------- 16-JUN-08 05.01.27.439000 PM -08:00 16-JUN-08 05.01.27.439000 PM 1 row selected. SQL> SQL> drop table t; Table dropped. SQL> SQL> --