Using c# or vb.net code the conversion is even more simple. An output column is needed because we type can not be changed on the fly, alternative is adding an input column on forehand make it ReadWrite.
Next code will fill the new column.
public override void Input0_ProcessInputRow(Input0Buffer Row)
{
if (Row.DataDate_IsNull)
Row.DataDateAsDate_IsNull = true;
else
{
DateTime tmp;
if (DateTime.TryParseExact(Row.DataDate.ToString(), "yyyyMMdd", new DateTimeFormatInfo(), System.Globalization.DateTimeStyles.None, out tmp))
Row.DataDateAsDate = tmp;
else
// throw exception or return null
Row.DataDateAsDate_IsNull = true;
}
}