FROM_TZ(x, time_zone) converts the TIMESTAMP x and time zone specified by time_zone to a TIMESTAMP WITH TIMEZONE. : FROM_TZ « Date Timestamp Functions « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Date Timestamp Functions
3. FROM_TZ

SQL>
SQL> SELECT FROM_TZ(TIMESTAMP '2005-05-13 07:15:31.1234', 'EST')
  2  FROM dual;

FROM_TZ(TIMESTAMP'2005-05-1307:15:31.1234','EST')
---------------------------------------------------------------------------
13-MAY-05 07.15.31.123400000 AM EST

SQL>