title: ORA-01830: date format picture ends before converting entire input string
body: <p>Can you please advise on this?</p>
  
  <pre><code>CREATE TABLE TEST2 ( 
  JOB_NAME VARCHAR2(50) NULL, 
  RUNTIME NUMBER(22) NULL, 
  STARTTIME1 VARCHAR2(50) NULL, 
  ENDTIME1 VARCHAR2(50) NULL, 
  STARTTIME_READ DATE NULL, 
  ENDTIME_READ DATE NULL 
  ) 
  GO 
  
  insert into TEST2 values ('TEST JOB',37,'08/18/2015 20:12:24','08/18/2015 20:13:01',null,null)
   go 
  insert into TEST2 values ('TEST JOB',37,'08/18/2015 20:12:24','08/18/2015 20:13:01',null,null)
   go 
  insert into TEST2 values ('TEST JOB',195,'08/20/2015 19:17:05','08/20/2015 19:20:20',null,null)
   go 
  insert into TEST2 values ('TEST JOB',171,'08/19/2015 19:16:52','08/19/2015 19:19:43',null,null)
   go 
  insert into TEST2 values ('TEST JOB',195,'08/21/2015 19:19:08','08/21/2015 19:22:23',null,null)
   go 
  insert into TEST2 values ('TEST JOB',32,'08/24/2015 19:23:52','08/24/2015 19:24:24',null,null)
   go 
  insert into TEST2 values ('TEST JOB',19,'08/26/2015 19:19:00','08/26/2015 19:19:19',null,null)
   go 
  insert into TEST2 values ('TEST JOB',92,'08/25/2015 19:18:59','08/25/2015 19:20:31',null,null)
   go 
  insert into TEST2 values ('TEST JOB',198,'08/27/2015 19:29:58','08/27/2015 19:33:16',null,null)
   go 
  insert into TEST2 values ('TEST JOB',19,'08/28/2015 19:18:13','08/28/2015 19:18:32',null,null)
   go 
  insert into TEST2 values ('TEST JOB',44,'08/31/2015 19:49:22','08/31/2015 19:50:06',null,null)
   go 
  insert into TEST2 values ('TEST JOB',266,'09/11/2015 19:17:10','09/01/2015 19:21:36',null,null)
   go 
  insert into TEST2 values ('TEST JOB',18,'09/20/2015 19:17:33','09/02/2015 19:17:51',null,null)
   go 
  insert into TEST2 values ('TEST JOB',33,'09/22/2015 19:16:50','09/03/2015 19:17:23',null,null)
   go 
  insert into TEST2 values ('TEST JOB',170,'08/17/2015 19:18:07','08/17/2015 19:20:57
  </code></pre>
  
  <p>query: </p>
  
  <pre><code>select job_name,to_char(to_date(avg(to_number(to_char(to_date(starttime1,'mm/dd/yyyy hh24:mi:ss'),'SSSSS'))),'SSSSS'),'HH24:MI:SS')AVG_STARTIME
   from TEST2 group by job_name 
  </code></pre>
  
  <p>Error: </p>
  
  <blockquote>
    <p>ORA-01830: date format picture ends before converting entire input string </p>
  </blockquote>
  
  <p>it is working for some records in the table. Those dates exactly looks like the above. I am not getting what is wrong with this date format</p>
  
  <p>Note: I am using oracle 8i</p>