use DateTime;
use DateTime::Format::Strptime;

my $strp = DateTime::Format::Strptime->new(
  pattern => '%a, %d %Y %H:%M:%S %z'
);
my $dt = $strp->parse_datetime('Sat, 20 Feb 2010 01:31:52 GMT');
$dt->add(days => 1);

$dt->set_formatter('%a, %d %Y %H:%M:%S %z');
my $date_string = "$dt";