use Date::Manip;

my $date = "2008-11-03 19:03:44";

Date_Init("TZ=EST");
my $http_date = UnixDate(ParseDate("$date -0612"), "%a, %d %b %Y %H:%M:%S %Z");

print "$http_date\n";    # Mon, 03 Nov 2008 20:15:44 EST