PHP/JS倒计时与服务器时间

我已经在php/javascript显示倒计时到日期的工作。

<?php date_default_timezone_set( "Europe/Berlin"); ?>
<script>
  var end = new Date('04/12/2013 9:0 PM');
  var _second = 1000;
  var _minute = _second * 60;
  var _hour = _minute * 60;
  var _day = _hour * 24;
  var timer;
  function showRemaining() {
    var now = <? php echo date('D M d Y H:i:s O') ?> ;
    var distance = end - now;
    if(distance < 0) {
      clearInterval(timer);
      document.getElementById('countdown').innerHTML = 'EXPIRED!';
      return;
    }
    var days = Math.floor(distance / _day);
    var hours = Math.floor((distance % _day) / _hour);
    var minutes = Math.floor((distance % _hour) / _minute);
    var seconds = Math.floor((distance % _minute) / _second);
    document.getElementById('countdown').innerHTML = days + 'd ';
    document.getElementById('countdown').innerHTML += hours + ':';
    document.getElementById('countdown').innerHTML += minutes + ':';
    document.getElementById('countdown').innerHTML += seconds;
  }
  timer = setInterval(showRemaining, 1000);
</script>

我试过了，但是没有成功