SQL> var v_d date;
Usage: VAR[IABLE] [ <variable> [ NUMBER | CHAR | CHAR (n [CHAR|BYTE]) |
                    VARCHAR2 (n [CHAR|BYTE]) | NCHAR | NCHAR (n) |
                    NVARCHAR2 (n) | CLOB | NCLOB | REFCURSOR |
                    BINARY_FLOAT | BINARY_DOUBLE ] ]
SQL> begin
  2      select Ordered_Date(sysdate) into :v_d  from dual;
  3   end;
  4  /
SP2-0552: Bind variable "V_D" not declared.

SQL> DECLARE
  2     v_date date;
  3  BEGIN
  4     v_date := Ordered_Date(sysdate);
  5     dbms_output.put_line('Today Date is : ' || v_date);
  6  END;
  7  /
Today Date is : 23-DEC-10

PL/SQL procedure successfully completed.

SQL> exec DBMS_OUTPUT.PUT_LINE (Ordered_Date(sysdate))
23-DEC-10

PL/SQL procedure successfully completed.

DECLARE 
    sometime DATE; 
BEGIN 
    sometime := Ordered_date(SYSDATE); 
END; 

/

select Ordered_date(SYSDATE) from dual

  1  DECLARE
  2      v_date DATE;
  3  BEGIN
  4      SELECT SYSDATE
  5      INTO   v_date
  6      FROM   dual;
  7      dbms_output.Put_line('Today Date is : '
  8                           || v_date);
  9* END;
 10  /
Today Date is : 25-NOV-14

PL/SQL procedure successfully completed.

SQL> var v_d date;
Usage: VAR[IABLE] [ <variable> [ NUMBER | CHAR | CHAR (n [CHAR|BYTE]) |
                    VARCHAR2 (n [CHAR|BYTE]) | NCHAR | NCHAR (n) |
                    NVARCHAR2 (n) | CLOB | NCLOB | REFCURSOR |