Question

Property AutoGenerateColumns is set in true.
Column with date could have different indexes.

        OracleDataAdapter adapter = new OracleDataAdapter();
        DataTable tableD = new DataTable();
        tableD.Locale = System.Globalization.CultureInfo.InvariantCulture;
        adapter.SelectCommand = oracleCom;
        adapter.Fill(tableD);
        tableResults.DataSource = tableD.AsDataView();
        tableResults.DataBind();

Columns with date type values are get from different tables in db. And they have different names.

Answer 1

I would use RowDataBound to format your columns.

protected void gridView1_RowDataBound(Object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DataRow row = ((DataRowView)e.Row.DataItem).Row;
        foreach (DataColumn col in row.Table.Columns)
        {
            if (col.DataType == typeof(DateTime))
            { 
                DateTime dt = row.Field<DateTime>(col);
                e.Row.Cells[col.Ordinal].Text = dt.ToString("D");
            }
        }
    }
}

Standard Date and Time Format Strings

If AutoGenerateColumns would set to false you could use the DataFormatString property on the BoundFields instead.