В мануале есть комментарий с проверочным примером:
<blockquote>The documentation should have this info. The function time() returns always timestamp that is timezone independent (=UTC).
<?php
date_default_timezone_set("UTC");
echo "UTC:".time();
echo "<br>";
date_default_timezone_set("Europe/Helsinki");
echo "Europe/Helsinki:".time();
echo "<br>";
?>
Local time as string can be get by strftime() and local timestamp (if ever needed) by mktime().</blockquote>
