You can set your cookie value containing expiry and get your expiry from cookie value.
// set
$expiry = time()+3600;
setcookie("mycookie", "mycookievalue|$expiry", $expiry);
// get
if (isset($_COOKIE["mycookie"])) {
list($value, $expiry) = explode("|", $_COOKIE["mycookie"]);
}
// Remember, some two-way encryption would be more secure in this case. See: https://github.com/qeremy/Cryptee