DB time zone are different from session time zone, this may caused by 1. default setting for sessiontimezon. 2. daylight saving not changed back automatically.
Question: How to set default session time zone. Oracle doc says set OS variable ORA_SDTZ, but all my other database servers do not have it setup and no any issue.
SQL> select dbtimezone,sessiontimezone,to_char(sysdate,'yyyymmdd hh24:mi:ss') from dual;
DBTIMEZONE SESSIONTIMEZONE TO_CHAR(SYSDATE,'
--------------- --------------- -----------------
-05:00 -06:00 20151105 17:00:36
SQL> !date
Thu Nov 5 17:00:43 CST 2015