time() returns correct value, but date('O') - incorrect timezone
date_default_timezone_set('Europe/Moscow');
echo date('d/m/Y H:i O'), "n";
echo 'timezone default: ', date_default_timezone_get(), "n";
echo 'timezone version: ', timezone_version_get();

05/11/2011 22:39 +0400
timezone default: Europe/Moscow
timezone version: 0.system

05/11/2011 23:17 +0400
timezone default: Europe/Moscow
timezone version: 2011.14