ORA-01861: literal does not match format string

Hi, I just seem to get this query against the alertlog to work, how should I change it?

SQL> select nvl(

(SELECT sumerrors ||' : '|| SUBSTR (SYS_CONNECT_BY_PATH (altext||':'||acnt||':'||trim(to_char(last_err_hours,'990.9')), ','), 2)

      FROM (select altext, acnt, round(24*(sysdate-last_err_date),1) last_err_hours, sum(acnt) over () sumerrors,ROW_NUMBER () OVER (ORDER BY altext ) rn, count(*) over () cnt from (

                SELECT regexp_substr(MESSAGE_TEXT,'ORA-\\d+') altext, COUNT (*) acnt,  to_date(to_char(max(originating_timestamp),'YYYY-MM-DD HH24:MI:SS'),'YYYY-MM-DD HH24:MI:SS') last_err_date