Connect by + date + to_char('DAY'); to_char('D')

Question

Why do these two statements create different results?
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
  SELECT closing_day,day_of_week,num_of_week
  FROM (
          SELECT
               TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL AS closing_day,
               TO_CHAR(TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL, 'D', 'NLS_DATE_LANGUAGE=AMERICAN') AS "NUM_OF_WEEK",
               TO_CHAR(TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL, 'DAY', 'NLS_DATE_LANGUAGE=AMERICAN') AS "DAY_OF_WEEK"
          FROM 
               dual
          CONNECT BY
               LEVEL < SYSDATE - TO_DATE('01-01-2010', 'DD-MM-YYYY')
  ) WHERE num_OF_WEEK NOT IN ('6','7');
  SELECT closing_day,day_of_week,num_of_week
  FROM (
          SELECT
               TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL AS closing_day,
               TO_CHAR(TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL, 'D', 'NLS_DATE_LANGUAGE=AMERICAN') AS "NUM_OF_WEEK",
               TO_CHAR(TO_DATE('01-01-2010', 'DD-MM-YYYY') + LEVEL, 'DAY', 'NLS_DATE_LANGUAGE=AMERICAN') AS "DAY_OF_WEEK"
          FROM 
               dual
          CONNECT BY
               LEVEL < SYSDATE - TO_DATE('01-01-2010', 'DD-MM-YYYY')
  ) WHERE day_OF_WEEK NOT IN ('SATURDAY','SUNDAY');

Answer 1

It's because using the format element 'D' means you depend on your NLS_TERRITORY settings. For example in my region of the world 6 = Friday and 7 = Saturday (week starts on Sunday here).
SQL> ALTER SESSION SET NLS_TERRITORY='GERMANY';
Session altered.
SQL> SELECT TO_CHAR(TO_DATE('11/04/2011','MM/DD/YYYY'),'D') FROM DUAL;
T
5
1 row selected.
SQL> ALTER SESSION SET NLS_TERRITORY='AMERICA';
Session altered.
SQL> SELECT TO_CHAR(TO_DATE('11/04/2011','MM/DD/YYYY'),'D') FROM DUAL;
T
6
1 row selected.