SQL & PL/SQL :: Display Time Format In Oracle By Create View

I am not able to find any information regarding inserting data with timestamp format without putting the date.

This is what i want to do:

ALTER SESSION SET NLS_TIMESTAMP_TZ_FORMAT='DD-MON-RR HH24:MI TZR';

I create the column data type as timestamp with time zone. This is value i have inserted:

Insert Into TEST Values('05-OCT-2013 01:00 +08:00','05-OCT-2013 23:00 +08:00','SCIENCE);

And now i wish to display it in 'HH24:MI TZR' only after i deduct both of the time. This is the view i have created:

Create View TESTRECRDS As Select (STARTTIME- ENDTIME)*24 As DURATION, Science;

But when i select it display as weird timing because it would default in 'DD-MON-RR HH24:MI TZR' format.

BUT IF i create the view and display as 'HH24:MI TZR', it would gives me error:

Create View TESTRECRDS As Select To_Char(STARTTIME- ENDTIME, 'HH24:MI TZR')*24 As DURATION, Science;

Error would be invalid number. How can i display only 'HH24:MI TZR' after subtracting?