Custom $wpdb returns unexpected time based results

Question

This may be your problem:

$wpdb->terms.slug = 'another-sample' OR $wpdb->terms.slug = 'sample' AND
//the date logic doesn't seem to qork quite right
$wpdb->posts.post_date > DATE_SUB( NOW(), INTERVAL 7 DAY)";

Your OR operator might be confusing the query. Try using parentheses:

($wpdb->terms.slug = 'another-sample' OR $wpdb->terms.slug = 'sample') AND
//the date logic doesn't seem to qork quite right
$wpdb->posts.post_date > DATE_SUB( NOW(), INTERVAL 7 DAY)";