ORA-08186: invalid timestamp specified

ORA-08186: invalid timestamp specified

while executing below query we got the following error message:

SELECT * FROM PN_SPACE_ASSIGN_CUST_ALL AS OF TIMESTAMP to_timestamp('03-10-2011 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.