팁에서 보고 해결 하였습니다.

확장변수명이 shotdate 입니다.

 <!-- // 확장변수로 정렬하기 위해 추가 시작 -->
<!--@if(!$sort_index)-->
    {@
        $noticeTF = false;
        if($module_info->except_notice == 'Y') $noticeTF = true;
        $args->module_srl = $module_info->module_srl;
        $args->list_count = $total_count;
        $args->category_srl = $category;
        $oDocumentModel = &getModel('document');
        $output = $oDocumentModel->getDocumentList($args, $noticeTF);
        $document_list = $output->data;
    }
    <!--@foreach($document_list as $no => $document)-->
        {@
            $extra_sortkey[$no] = $document->getExtraEidValue('shotdate');
            $extra_sortkey2[$no] = $no;
        }
    <!--@end-->
    {@
        array_multisort($extra_sortkey, $extra_sortkey2, $document_list);
        if($module_info->order_type == 'asc' || $order_type == 'asc') $document_list = array_reverse($document_list);
    }
    <!--@if($document_srl)-->
        <!--@foreach($document_list as $document)-->
            {@
                $extra_doc_srl[] = $document->document_srl;
            }
        <!--@end-->
        {@
            $page = ((int) (array_search($document_srl, $extra_doc_srl) / $module_info->list_count)) + 1;
        }
    <!--@end-->
    {@
        $document_list = array_slice($document_list, $module_info->list_count * ($page-1), $module_info->list_count, true);
    }
<!--@end-->
<!-- // 확장변수로 정렬하기 위해 추가 끝 -->