What is the scope/purpose of converting it because, you can't do it in the dataadaptar, therefore inside the datatable you can search for the date column and change the datatype.
Like for example
foreach (DataColumn cl in dt.Columns)
{
if (cl.ColumnName.ToUpper().Contains("DATE"))
cl.DataType = typeof(DateTime);
}
Or you can convert the data with data.ToString() / Convert.ToString(data).
Hope i have understood you and would help you solve the problem you are facing.