Well we wouldn't want you to do that now ... 
Try this ... open includes/functions/functions_lookups.php and make sure the following is somewhere in this file. It's the main declaration for this function and is used elsewhere in Zen.
Code:
// build date range for new products
function zen_get_new_date_range($time_limit = false) {
if ($time_limit == false) {
$time_limit = SHOW_NEW_PRODUCTS_LIMIT;
}
// 120 days; 24 hours; 60 mins; 60secs
$date_range = time() - ($time_limit * 24 * 60 * 60);
$upcoming_mask_range = time();
$upcoming_mask = date('Ymd', $upcoming_mask_range);
// echo 'Now: '. date('Y-m-d') ."<br />";
// echo $time_limit . ' Days: '. date('Ymd', $date_range) ."<br />";
$zc_new_date = date('Ymd', $date_range);
switch (true) {
case (SHOW_NEW_PRODUCTS_LIMIT == 0):
$new_range = '';
break;
case (SHOW_NEW_PRODUCTS_LIMIT == 1):
$zc_new_date = date('Ym', time()) . '01';
$new_range = ' and p.products_date_added >=' . $zc_new_date;
break;
default:
$new_range = ' and p.products_date_added >=' . $zc_new_date;
}
if (SHOW_NEW_PRODUCTS_UPCOMING_MASKED == 0) {
// do nothing upcoming shows in new
} else {
// do not include upcoming in new
$new_range .= " and (p.products_date_available <=" . $upcoming_mask . " or p.products_date_available IS NULL)";
}
return $new_range;
}
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