why can't I retrieve the comment ID?

Question

I wrote a function to update the comment time when a comment goes form unapproved to approved:

function ji_update_comment_date($comment){
$commentarr = array(
                'comment_ID'=>comment_ID(),
                //this is where it fails me,I can't get the ID
                'comment_date'=>date("Y-m-d H:i:s"),
                'comment_date_gmt'=> date("Y-m-d H:i:s") 
                );

        wp_update_comment( $commentarr );}
add_action('comment_unapproved_to_approved','ji_update_comment_date');

SO the comment_ID() is not working ,I can't seem to get it otherwise my code works perfectly.

Answer 1

So @Jack Johansson and @Dave Romsey helped me to make it work.So I will put the solution here:

function ji_update_comment_date($comment,$commentarr){

$comment = get_comment( $comment );
$commentarr = array(
                'comment_ID'=>$comment->comment_ID,
                'comment_date'=>date("Y-m-d H:i:s"),
                'comment_date_gmt'=> date("Y-m-d H:i:s") 
                );

        wp_update_comment( $commentarr         );}
add_action('comment_unapproved_to_approved','ji_update_comment_date');

I don't understand why comment_ID() and get_comment_ID() won't work in this scenario. But get_comment is surely a workaround.