<?PHP
function cnvrt($date){
    $b = new DateTime($date);
    return $b->format('U');
}

echo cnvrt("Tue, 26 Oct 2010 18:31:27 MDT"); //1288139487
echo "<br>";
echo cnvrt("Tue, 26 Oct 2010 00:31:27 GMT"); //1288053087
?>