I\'ve asked a very similar question before but got no answers that helped.
I have a site that allows users to post notes. There will be a time stamp on those notes.
You could use PHPs DateTime and DateTimeZone to convert the datetime into the users current timezone:
http://www.php.net/manual/de/class.datetime.php
http://www.php.net/manual/de/class.datetimezone.php
$date = new DateTime($dateTimeFromDB);
$date->setTimeZone( new DateTimeZone('User/Timezone') );
echo $date->format('d.m.Y H:i');