Diese Funktion ist ein Alias für: DateTime::setTimezone()
Return Value
Returns NULL on success or FALSE on failure.
Example
Following is the usage of this function:
<?php
   $dateSrc = '2007-04-19 12:50 GMT';
   $dateTime = date_create( $dateSrc);
   $DateTimeZone = timezone_open ( 'America/Chicago' );
   date_timezone_set( $dateTime, $DateTimeZone );
   $NewDateTimeZone = date_timezone_get($dateTime);
   echo 'New timeZone is '. timezone_name_get($NewDateTimeZone);
   echo "\n";
   # Using second function.
   $dateTime = new DateTime($dateSrc);
   $DateTimeZone = timezone_open ( 'America/Chicago' );
   $dateTime->setTimezone( $DateTimeZone );
   $NewDateTimeZone = $dateTime->getTimezone ();
   echo 'New timeZone is '. timezone_name_get ($NewDateTimeZone);
?> 
This will produce following result:
New timeZone is America/Chicago
New timeZone is America/Chicago