select to_char(trunc(sysdate),'DD-MM-YYYY HH24:MI:SS')
from   dual;

SQL> select trunc(sysdate) c_start,
  2         (trunc(sysdate) + 1) - 1/(24*60*60) c_end
  3  from dual;

C_START             C_END
------------------- -------------------
06.02.2013 00:00:00 06.02.2013 23:59:59

SQL>

WITH TEMP AS
  (SELECT TO_DATE('06-FEB-2013 23:59:59','DD-MON-YYYY HH24:MI:SS') SOMEDATE
  FROM DUAL
  )
SELECT somedate
FROM temp
WHERE somedate >=TRUNC(SYSDATE)
AND somedate    <TRUNC(SYSDATE)+1;