anchor.diff:  	ets:insert(?MODULE, {rfc1123, B}),
   	{ok, #state{universaltime=T, rfc1123=B, tref=TRef}}.
   
  --spec handle_call(any(), _, State)
  -	-> {reply, ignored, State} | {stop, normal, stopped, State}
  +-type from() :: {pid(), term()}.
  +-spec handle_call
  +	(stop, from(), State) -> {stop, normal, stopped, State}
   	when State::#state{}.
   handle_call(stop, _From, State=#state{tref=TRef}) ->
  -	{ok, cancel} = timer:cancel(TRef),
   	{stop, normal, stopped, State};
   handle_call(_Request, _From, State) ->
   	{reply, ignored, State}.
  
positive.code: -record(state, {
  	universaltime = undefined :: undefined | calendar:datetime(),
  	rfc1123 = <<>> :: binary(),
  	tref = undefined :: undefined | timer:tref()
  }).
  
  %% API.
  
negative.code: -spec handle_info(any(), State) -> {noreply, State} when State::#state{}.
  handle_info(update, #state{universaltime=Prev, rfc1123=B1, tref=TRef0}) ->
  	%% Cancel the timer in case an external process sent an update message.
  	_ = erlang:cancel_timer(TRef0),
  	T = erlang:universaltime(),
  	B2 = update_rfc1123(B1, Prev, T),
  	ets:insert(?MODULE, {rfc1123, B2}),
  