DiscountMeta
$meta_query = array( 'relation' => 'AND', array( 'key' => 'discount_listing_id', 'value' => '1568,1679,1851', 'compare' => 'IN', ), array( 'key' => 'discount_start', 'value' => '$timenow', 'compare' => '>=', ), array( 'key' => 'discount_end', 'value' => '$timenow', 'compare' => '<=', ), );