Why is Cookie changing in WP?

Question

HTTP Cookies

There is such code in function.php

function app_output_buffer() {
    ob_start();
}
add_action('init', 'app_output_buffer');

add_action( 'wp_head', 'home' );
function home() {
  //Если пост имеет метку город и это не основная страница блога - ставим куку
  if (has_term('gorod', 'post_tag') and !(is_home())) {
        setcookie('city',get_page_uri(), time()+1209600, COOKIEPATH, COOKIE_DOMAIN, false);
    }
}

Everything works, the page starts loading - the cookie is assigned, but after half a second before the end of the full load, the cookie changes to the last blog entry.