DevExpressPivotCustomSort

private void pivotGrid_CustomFieldSort(object sender, PivotGridCustomFieldSortEventArgs e)
{
    if (e.Field.FieldName == "MONTH")
    {
                if (e.Value1 == null || e.Value2 == null) return;
                e.Handled = true;
                DateTime d1 = Convert.ToDateTime("1 " + e.Value1.ToString() + " 1900");
                DateTime d2 = Convert.ToDateTime("1 " + e.Value2.ToString() + " 1900");
                if (d1 > d2)
                    e.Result = 1;
                else if (d1 == d2)
                    e.Result = 0;
                else
                    e.Result = -1;
    }
}