Getting errorl in birthdatedate column in ssis package

Hi ,
In my SSIS package I am deriving birth date column by using below 

CASE WHEN Col015 IS NULL THEN Col015 ELSE CAST(SUBSTRING(Col015,1,2) + '/' + SUBSTRING(Col015,3,2) + '/' + SUBSTRING(Col015,5,2) AS DATETIME) END AS BirthDate

by using above Ia ma getting data like 11/18/58

and in my destination table birthdate datatype is datetime.
when I am running my package may package gets failed 

error
[OLE DB Destination [227]] Error: There was an error with OLE DB Destination.Inputs[OLE DB Destination Input]. Columns[BirthDate] on OLE DB Destination.Inputs[OLE DB Destination Input]. 
The column status returned was: "The value could not be converted because of a potential loss of data.".

please help me to get rid out of this issue


regards,
Vipin Jha 

Thankx & regards, Vipin jha MCP