如何将ZF2 Doctrine createQueryBuilder日期字段转换为时区

This is my query :

$casesData = $this->getEntityManager()->getRepository('Cases\Entity\Cases')
    ->createQueryBuilder('cases')
    ->select('cases.CaseId',
        'cases.CreatedDate',
        'cases.LeadId',
        'cases.InquiryID',
        'cases.FirstName',
        'cases.LastName',
        'cases.CityDoc1',
        'cases.StateDoc1',
        'cases.SSN',
        'cases.Status',
        'cases.CaseManagerId',
        'users.first_name'
);

cases.CreatedDate is currently have "US Canada" timezone, now I want to convert base on timezone dropdown value, and I can't found any solution to convert timezone as per above query, please help me.

Actually with query builder you can't change the time zone, you have to use loop as doctrine return datetime object than you can modify the time as you wish

foreach($data as item){
   $date = $item['CreatedDate']->modify('....')
}