Calculate difference between 2 date / times in Oracle SQL

Answer

with tbl_demo AS
    (SELECT TO_DATE('11/26/2013 13:18:50', 'MM/DD/YYYY HH24:MI:SS') dt1
   , TO_DATE('11/28/2013 21:59:12', 'MM/DD/YYYY HH24:MI:SS') dt2
     FROM dual)
SELECT dt1
     , dt2
     , round(dt2 - dt1,2) diff_days
     , round(dt2 - dt1,2)*24 diff_hrs
     , numtodsinterval((dt2 - dt1),'day') diff_dd_hh_mm_ss
  from tbl_demo;