Modification post's tweet

When I update the past post, this plugin always tweet.
I want the option to tweet only in the new post if possible.

I have following fixes tentatively.

_do_tweet()
$limit = current_time( ‘timestamp’ ) – 2 * 3600;
if ( mysql2date( ‘Y-m-d’, $post->post_date ) < date( ‘Y-m-d’, $limit ) ) {
return false;
}

http://wordpress.org/extend/plugins/simple-tweet/