useTimer.js

const convertTimeDiff = diff => ({
  dd: Math.floor(diff / (1000 * 60 * 60 * 24)),
  hh: Math.floor((diff % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60)),
  mm: Math.floor((diff % (1000 * 60 * 60)) / (1000 * 60)),
  ss: Math.floor((diff % (1000 * 60)) / 1000)
});

const useTimer = timestamp => {
  const [timer, setTimer] = useState(null);

  useEffect(() => {
    const intervalId = setInterval(() => {
      setTimer(convertTimeDiff(timestamp - Date.now()));
    }, 1000);

    setTimer(convertTimeDiff(timestamp - Date.now()));

    return () => clearInterval(intervalId);
  }, [timestamp]);

  return timer;
};