Convert HTTP Header Last Modification Date to Integer

snoopy class can retrieve the specific page's lat modification date in
String
but is there any way to get into the integer or long?
>
<?php
include( "Snoopy.class.php" );
>
>
$request = new Snoopy;
$request->fetch( "http://www.mysite.com" );
>
>
if( ! $request -error ){
while( list( $key, $val ) = each( $request -headers ) ) {
echo $key.": ".$val."<br>\n";
}
}
?>