$re = '`(\d+/\d+/\d+) +((1[0-2]|0?[1-9]):([0-5][0-9]) ?([AaPp][Mm]))(?= +\d)`m';
$str = 'of Los Angeles 12/19/2018 11:39 AM She
as a Unit 1/18/2019 8:30 AM 4 1.';
preg_match_all($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