$config['time_reference'] = 'gmt';
//기본값이 local로 되어 있습니다.

//제 경우엔 autoload에 선언
$this->load->helper('date');

$time = now(); //위의 time_referense 가 gmt 이므로 gmt timestamp를 반환합니다.

//hook으로 구현한 내용입니다. 꼼수. ^^

        ob_start();
 ?>
 <script language="javascript" type="text/javascript">
  now = new Date();
  localtime = now.getTimezoneOffset();
  [removed](localtime);
 </script>
 <?php
 $g = ob_get_contents();
 ob_end_clean();

 define('GMT_DIF', $g);

         /**
  * gmt timestamp 를 local timestamp 변환
  * 
  * @author Jongwon Byun <codeigniterk@gmail.com>
  * @param string $time : gmt timestamp
  * @param string $daylight_saving : 섬머타임
  * @return string $local_timestamp : local 기준으로 변환된 timestamp
  */
 function gmt_2_local($time, $daylight_saving='false') 
  {
   //hook에서 선언한 gmt와 local의 시간차이에 따른 타임존 구하기
   switch (GMT_DIFF) 
     {
      case ('720'):
    $time_zone = 'UM12'; 
        break;
        case ('660'):
    $time_zone = 'UM11'; 
        break;
        case ('600'):
    $time_zone = 'UM10'; 
        break;
        case ('540'):
    $time_zone = 'UM9'; 
        break;
        case ('480'):
    $time_zone = 'UM8'; 
        break;
        case ('420'):
    $time_zone = 'UM7'; 
        break;
        case ('360'):
    $time_zone = 'UM6'; 
        break;
        case ('300'):
    $time_zone = 'UM5'; 
        break;
        case ('240'):
    $time_zone = 'UM4'; 
        break;
        case ('210'):
    $time_zone = 'UM35'; 
        break;
        case ('180'):
    $time_zone = 'UM3'; 
        break;
        case ('120'):
    $time_zone = 'UM2'; 
        break;
        case ('60'):
    $time_zone = 'UM1'; 
        break;
        case ('0'):
    $time_zone = 'UTC'; 
        break;
        case ('-60'):
    $time_zone = 'UP1'; 
        break;
        case ('-120'):
    $time_zone = 'UP2'; 
        break;
        case ('-180'):
    $time_zone = 'UP3'; 
        break;
        case ('-210'):
    $time_zone = 'UP35'; 
        break;
        case ('-240'):
    $time_zone = 'UP4'; 
        break;
        case ('-270'):
    $time_zone = 'UP45'; 
        break;
        case ('-300'):
    $time_zone = 'UP5'; 
        break;
        case ('-330'):
    $time_zone = 'UP55'; 
        break;
        case ('-360'):
    $time_zone = 'UP6'; 
        break;
        case ('-420'):
    $time_zone = 'UP7'; 
        break;
        case ('-480'):
    $time_zone = 'UP8'; 
        break;
        case ('-540'):
    $time_zone = 'UP9'; 
        break;
        case ('-570'):
    $time_zone = 'UP95'; 
        break;
        case ('-600'):
    $time_zone = 'UP10'; 
        break;
        case ('-660'):
    $time_zone = 'UP11'; 
        break;
        case ('-720'):
    $time_zone = 'UP12'; 
        break;
     }
     
     $local_timestamp = gmt_to_local($time, $time_zone, $daylight_saving);
   
   return $local_timestamp;
  }

$local_timestamp = gmt_2_local($gmt_timestamp);