gistfile1.txt

<?php

$cycles = pow(10, 5);

echo "Execution times for $cycles iterations:" . PHP_EOL;

$code = '$newDate = clone $date;';
measure($cycles, $code);
$code = '$newDate = new DateTime($timestamp, $timezone);';
measure($cycles, $code);

function measure($cycles, $code)
{
        echo $code . PHP_EOL;
        $startClone = microtime(true);
        $date = new DateTime('now', new DateTimeZone('Europe/Budapest'));
        $timestamp = '@' . $date->format('U');
        $timezone = $date->getTimezone();
        for ($i = 0; $i < $cycles; $i++)
        {
                eval($code);
        }
        echo microtime(true) - $startClone . PHP_EOL;
}

$ php test.php 
Execution times for 100000 iterations:
$newDate = clone $date;
0.4895339012146
$newDate = new DateTime($timestamp, $timezone);
1.9592518806458