I just upgraded to SQL Navigator 6.5 from 6.4.
SQL Navigator for Oracle 6.5 does not fire ALTER SESSION SET nls_date_format= using the format customer specifes in the session preferences.
WORKAROUND:
STATUS:
Waiting for fix in a future version of SQL Navigator for Oracle.
SQL Navigator for Oracle 6.5 uses the date format setting in the database which one can find out the format by running: select to_char(sysdate) from dual