If you stored your date in BD (whatever that is) in a more standard format, such as yyyy-mm-dd hh:mm:ss (MySQL style) or even mm/dd/yyyy hh:mm:ss, solving your problem and avoiding future ones would be much simpler.
For example, if you used a standard format, you could do this:
$offset = date('Z', strtotime($BD_date));
$user_date = date(Y-m-d H:i:s', strtotime($BD_date . $offset . ' seconds'));
Otherwise, you'll need to do some string-parsing code gymnastics.
