Handling Null Date in SSIS Derived Column

To Replace Null Value with Current Date:

ISNULL((DT_DBTIMESTAMP)SUBSTRING((DT_STR,30,1252)modifiedon,1,10)) ? (DT_DBTIMESTAMP)SUBSTRING((DT_STR,30,1252)GETDATE(),1,10) : (DT_DBTIMESTAMP)SUBSTRING((DT_STR,30,1252)modifiedon,1,10)

The below conversion replace null value with 'Null' instead of allowing column to insert default '1900-01-01....' value.

ISNULL((DT_DBTIMESTAMP)SUBSTRING((DT_STR,30,1252)PromisedShipDate,1,10)) ? NULL(DT_DATE) : (DT_DBTIMESTAMP)SUBSTRING((DT_STR,30,1252)PromisedShipDate,1,10)