This Oracle tutorial explains how to use the Oracle/PLSQL DBTIMEZONE function.
DBTIMEZONE returns the time zone for the database in the following format: '[+|-]TZH:TZM' or a time zone region name.
The syntax for the Oracle/PLSQL DBTIMEZONE function is:
DBTIMEZONE
There are no parameters for the DBTIMEZONE function.
SQL> select DBTIMEZONE from dual;
DBTIME
------
+00:00
SQL>