WP-Cal Hack – PHP help

I am trying to use the old plugin WP-Cal, but the plugin uses an old function:

user_can_edit_post

which is in the code:

if(user_can_edit_post($user_ID, $post->ID)){
$canedit = true;
echo “Add event<div class=’clear’></div>”;
}

Originally, the code only let admins edit, but since the function is no longer used, it makes it so that anyone can edit. How would I change this so that only the administrator is allowed to do this using the functions which are supported now?