Limit popular posts by days

Here is a function which show the posts of last 7days or you can change it according to your requirement.

function filter_where($where="") {
        //posts in the last 7 days
        $where .= " AND post_date > '" . date('Y-m-d', strtotime('-7 days')) . "'";
        return $where;
}
add_filter('posts_where', 'filter_where');