You can use the $WPDB query to query the DB, an example would be:
$editedposts = $wpdb->get_results(
"
SELECT ID, post_title
FROM $wpdb->posts
WHERE post_modified = between DateAdd(DD,-7,GETDATE() ) and GETDATE()
"
);
This lists all posts which have been edited in the last 7 days (not tested), you would do something similar to get posts created in that date:
$newposts = $wpdb->get_results(
"
SELECT ID, post_title
FROM $wpdb->posts
WHERE post_date = between DateAdd(DD,-7,GETDATE() ) and GETDATE()
"
);
You can then query the data using the variable e.g.
foreach ( $editedposts as $newposts ) {
echo $newposts->post_title;
}