I was able to do this.
you have to add the folowing to your sql database(be sure to backup first!)
INSERT INTO `configuration` (`configuration_id`, `configuration_title`, `configuration_key`, `configuration_value`, `configuration_description`, `configuration_group_id`, `sort_order`, `last_modified`, `date_added`) VALUES (250, 'Display Product Last Updated', 'PRODUCT_LIST_LAST_MODIFIED', '5', 'Do You want to display the date an item was last updated?', 8, 90, '2011-07-19 17:33:42', '2011-07-19 11:07:11');
open catalog/index.php
------------------------------------------
find:
'PRODUCT_LIST_QUANTITY' => PRODUCT_LIST_QUANTITY,
below add:
'PRODUCT_LIST_LAST_MODIFIED' => PRODUCT_LIST_LAST_MODIFIED,
------------------------------------------
find:
case 'PRODUCT_LIST_QUANTITY':
$select_column_list .= 'p.products_quantity, ';
break;
below add:
case 'PRODUCT_LIST_LAST_MODIFIED':
$select_column_list .= 'p.products_last_modified, ';
break;
------------------------------------------
find:
case 'PRODUCT_LIST_QUANTITY':
$listing_sql .= " order by p.products_quantity " . ($sort_order == 'd' ? 'desc' : '') . ", pd.products_name";
break;
Below add:
case 'PRODUCT_LIST_LAST_MODIFIED':
$listing_sql .= " order by p.products_last_modified " . ($sort_order == 'd' ? 'desc' : '') . ", pd.products_name";
break;
******************************************
open catalog/includes/modules/product_listing.php
------------------------------------------
find:
case 'PRODUCT_LIST_QUANTITY':
$lc_text = TABLE_HEADING_QUANTITY;
$lc_align = 'left';
break;
below add:
case 'PRODUCT_LIST_LAST_MODIFIED':
$lc_text = TABLE_HEADING_LAST_MODIFIED;
$lc_align = 'left';
break;
------------------------------------------
find:
case 'PRODUCT_LIST_QUANTITY':
$prod_list_contents .= ' <td align="right">' . $listing['products_quantity'] . '</td>';
break;
below add:
case 'PRODUCT_LIST_LAST_MODIFIED':
$prod_list_contents .= ' <td align="left">' . $listing['products_last_modified'] . '</td>';
break;
------------------------------------------
open catalog/includes/languages/english/index.php
add:
define('TABLE_HEADING_LAST_MODIFIED', 'Last Modified');
Done.
hope it works for you!!