<?php
	$string = "01 Jan 2004 blah blah 02 Jan 2004 and blah 03 Jan 2004 and who even cares about 31 Dec 2050? I know that I don't.";
	$string = preg_replace("/([1-9]|[0-2][0-9]|3[0-1]) (Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec) [0-9]{4}/", " ", $string);
	var_dump($string);
?>

string(73) "  blah blah   and blah   and who even cares about  ? I know that I don't."