$re = '/(?<=Sent: Monday, |Tuesday, |Wednesday, |Thursday, |Friday, |Saturday, |Sunday, )(\d\d\s|\d\s)(January |February |March |April |May |June |July |August |September |October |November |December )(20\d\d)/m';
$str = 'From: john@workplace.com
Sent: Thursday, 23 May 2019 7:14 AM
To: Team Inbox
Subject: Send me some more cookies';
preg_match_all($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