0 - 3 of 3 tags for invalid date

AND CAST (contact_date AS DATE  FORMAT 'dd/mm/yyyy') <=CAST ({?StartDATE} AS DATE FORMAT 'dd/mm/yyyy')
Above code returns error - Failed 2666: Invalid Date Supplied for contact_date

Hi all,
I have a column(say date_col) which is integers and contains values which can or cannot be converted into date type. now i have to select the NOT-CONVERTABLE values as "NULL" and CAST the convertable values into DATE(May be Using a case statement). Can some one help me as how to accomplish this??
P.S-> I am using Teradata 14.0

Hi All,
I am trying to port data from a flat file to TD via BTEQ.
The table definition is :