Insert this code at the top of the page:
<?php
$mtime = microtime();
$mtime = explode(" ", $mtime);
$starttime = $mtime[1] + $mtime[0];
?>
Then at the bottom of the page add the following:
<?php
$mtime = microtime();
$mtime = explode(" ", $mtime);
$endtime = $mtime[1] + $mtime[0];
$totaltime = ($endtime - $starttime);
echo "This page was created in $totaltime seconds.";
?>