$re = '/<(\w*[dD]ate\w*)>\d{13}<\/\1>/m';
$str = '<dateCreated>1619155581543</dateCreated>
<dispatchDate>1619478000000</dispatchDate>
<deliveryDate>1619564400000</deliveryDate>
<thirteendigits>1619564400000</thirteendigits>';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($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