I pull a lot of dates in the format of MMDDYYYY in from text files in SSIS.  I typically use something like the following as a new DT_DATE (rather than DT_DBTIMESTAMP) column in a Derived Column transformation:

LEN(TRIM(FromDate)) == 0 ? NULL(DT_DATE) : (DT_DATE)(SUBSTRING(FromDate,1,2) + "/" + SUBSTRING(FromDate,4,2) + "/" + SUBSTRING(FromDate,6,4))