Why not use the built in DateTime/TimeZone functionality?
<?php
$mysqlDate="2009-04-01 15:36:13";
$dateTime = new DateTime ($mysqlDate);
$dateTime->setTimezone(new DateTimeZone('America/Los_Angeles'));
?>
DateTime Class: http://us3.php.net/manual/en/class.datetime.php
DateTimeZone Class: http://us3.php.net/manual/en/class.datetimezone.php
PHP’s supported Timezones: http://php.net/manual/en/timezones.php