// Add a column to the posts and pages list in the admin panel to display the last modified date
function add_last_modified_column($columns) {
    $columns['last_modified'] = 'Last Modified';
    return $columns;
}
add_filter('manage_posts_columns', 'add_last_modified_column');
add_filter('manage_pages_columns', 'add_last_modified_column');

// Populate the last modified column with the date and time
function display_last_modified_column($column, $post_id) {
    if ($column == 'last_modified') {
        $last_modified = get_post_modified_time('F j, Y, g:i a', false, $post_id);
        echo $last_modified;
    }
}
add_action('manage_posts_custom_column', 'display_last_modified_column', 10, 2);
add_action('manage_pages_custom_column', 'display_last_modified_column', 10, 2);

// Make the last modified column sortable
function make_last_modified_column_sortable($columns) {
    $columns['last_modified'] = 'last_modified';
    return $columns;
}
add_filter('manage_edit-post_sortable_columns', 'make_last_modified_column_sortable');
add_filter('manage_edit-page_sortable_columns', 'make_last_modified_column_sortable');

// Set the sorting logic for the last modified column
function sort_by_last_modified($vars) {
    if (isset($vars['orderby']) && 'last_modified' == $vars['orderby']) {
        $vars = array_merge($vars, array(
            'orderby' => 'modified'
        ));
    }
    return $vars;
}
add_filter('request', 'sort_by_last_modified');