Clarify timestamp. Closes #6438

Author: chrismccord

lib/phoenix/token.ex

@@ -152,7 +152,7 @@ defmodule Phoenix.Token do
     * `:key_digest` - option passed to `Plug.Crypto.KeyGenerator`
       when generating the encryption and signing keys. Defaults to `:sha256`
     * `:signed_at` - set the timestamp of the token in seconds.
-      Defaults to `System.os_time(:millisecond)`
+      Defaults to `System.os_time(:second)`
     * `:max_age` - the default maximum age of the token. Defaults to
       86400 seconds (1 day) and it may be overridden on `decrypt/4`.