first day of week

Hi,  we have an application written on forms 12c on weblogic 12 on  Windows 2012 data center.

we decide first day of week  like below in forms procedure. it returns monday.  we want to see sunday  as first day of week.

select to_char(sysdate,'D') from dual;

I m trying lot of options;   i m adding NLS_TERRITORY=AMERICA in default.env  and regedit. I m changing  regional settings to English(United States). I m changing first day of week as sunday  on  OS Level.

Nothing changes.  How  the forms inherits first day of week ?  what do i need to change first day of week ?