setAge example

$customer->setSalutation($data['__customer_salutation']);
        $customer->setFirstname($data['__customer_firstname']);
        $customer->setLastname($data['__customer_lastname']);
        $customer->setNumber($data['__customer_customernumber']);
        $customer->setNewsletter((bool) $data['__active_campaign']);

        if ($data['__customer_birthday']) {
            $customer->setBirthday(new DateTime($data['__customer_birthday']));
        }

        if ($customer->getBirthday()) {
            $customer->setAge($customer->getBirthday()->diff(new DateTime())->y);
        }

        if (!empty($data['__customer_lockeduntil'])) {
            $customer->setLockedUntil(new DateTime($data['__customer_lockeduntil']));
        }
        if (!empty($data['__customer_firstlogin'])) {
            $customer->setFirstLogin(new DateTime($data['__customer_firstlogin']));
        }
        if (!empty($data['__customer_lastlogin'])) {
            $customer->setLastLogin(new DateTime($data['__customer_lastlogin']));
        }