ORA-08186: invalid timestamp specified

ORA-Errors
While executing below query i got the following error message:
SELECT * FROM PN_SPACE_ASSIGN_CUST_ALL
 AS OF TIMESTAMP to_timestamp(’03-10-2014 08:00:00′,’dd-mm-yyyy HH24:MI:SS’)
ERROR at line 1:
ORA-08186: invalid timestamp specified
Reason: Because NLS_DATE_FORMAT doesn’t set.
 
Solution: set NLS_DATE_FORMAT
 
ALTER SESSION SET nls_date_format = ‘dd-mm-yyyy hh24:mi:ss’;
 
retest.