Manejo de fechas en Oracle

[Princesa_tuza]

ORACLE_HOME=/u01/app/oracle/product/9.2.0
export ORACLE_HOME

este es el script
set echo off;
set heading off;
set feedback off;
set linesize 300;
set pagesize 1000;

select to_date(to_char(d.thedate))||','||to_char(b.name) ||',' ||to_char(c.name)||','||to_char(a.value)||','||
to_char(f.name)||','||to_char(e.svalue)
from twtdatavalues a
inner join twtinstances b on b.id = a.insid
inner join twtindicators c on c.id = a.indid
inner join twttimes d on d.id = a.timeid
left outer join twtpropvalues e on e.insid = b.id
inner join twtproperties f on f.id = e.propid
where b.name like 'int%'
AND d.thedate = TO_DATE(TO_CHAR (sysdate,'dd/mm/yy'))-1
order by a.timeid,a.insid,a.indid,e.propid;