Only just started poking in the vB code - but to me im just confused over where edit_date and edit_time come from ? your just linking edit_dateline.
I know dates are stored in unix format in the db so when you pull something out you'll need to parse it with the vbdate function
these two lines in class_postbit.php leaped out on a grep.
Code:
$this->post['postdate'] = vbdate($this->registry->options['dateformat'], $this->post['dateline'], true);
$this->post['posttime'] = vbdate($this->registry->options['timeformat'], $this->post['dateline']);
but I have no idea where you go next.