$re = '/./m';
$str = 'Right Ones
01/01/2000
1/1/2000
01/Jan/2000
31/01/2000
31/Jan/2000
31.Jan.2000
31-Jan-12
31-Jan-1983
28/02/2001
01/1/2000
01/Jan/2000
01/1/01
01/Jan/01
29/02/2000
29/Feb/2000
01/01/2020 #1st Jan
07/03/2020 #3 July
12/2/2020 #2 December
23/4/2020 #23 April
Wrong Ones
31/04/2000
29/Feb/2001
13/13/2000
30/Feb/2000
25/February/2000
32/01/2000
32/Jan/2000
';
preg_match_all($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