Change timezone display format in user edit page
You can do it with below code 

    function yourcustomodulename_form_alter(&amp;$form, &amp;$form_state, $form_id) {
    if($form_id=='user_profile_form'){
 $form['#after_build'][] = 'yourmodulename_after_build'; 

    }
    }
function yourmodulename_after_build($form, &amp;$form_state) { 
      $options = array();
      foreach(timezone_identifiers_list() as $timezone) {
        //$options[$timezone] sets the value for date_default_timezone select
        //$timezone set the display for select
        $options[$timezone] = $timezone;
      }
      $form['account']['timezone']['timezone']['#options'] = $options;
return $form;
}