$re = '/^(0?[1-9]|1[012])\/(0?[1-9]|[12]\d|3[01])\/[12]\d{3} ([01]\d|2[0-3])\:[0-5]\d\:[0-5]\d$/';
$str = '
2/2/2013 00:00:00
2/2/2013 12:30:20';
preg_match($re, $str, $matches, PREG_OFFSET_CAPTURE, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php