Correct ... your format is fine.
The conversion (strtotime) is only for calculation.
Like this example:
PHP Code:
<?php
$time1="24-11-2010 11:6:57";
$time2="24-11-2010 19:4:35";
// difference in seconds
$diff=abs(strtotime($time1)-strtotime($time2));
// difference in hours (rounded up).
echo intval($diff/3600);
?>