$re = '/(.*?),.*?((?:(?:[0-2]?\d{1})|(?:[3][01]{1}))[-:\/.](?:[0]?[1-9]|[1][012])[-:\/.](?:(?:[1]{1}\d{1}\d{1}\d{1})|(?:[2]{1}\d{3})))(?![\d]).*?((?:(?:[0-1][0-9])|(?:[2][0-3])|(?:[0-9])):(?:[0-5][0-9])(?::[0-5][0-9])?(?:\\\\s?(?:am|AM|pm|PM))?)/';
$str = 'MiƩrcoles, 30.12.2015 13:20:09';
preg_match($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