Refactor states with hooks

You are using a functional component u can only use Hooks. React.state is only for class components. If you want your intial React.state initialize it like this

const [timers, setTimers] = useState([
  {
    id: UUID.v4(),
    activity: "Testing activity",
    description: "Lorem ipsum kraf maga",
    elapsed: "0",
    runningSince: Date.now(),
  },
  {
    id: UUID.v4(),
    activity: "Next activity",
    description: "Lorem ipsum kung fu",
    elapsed: "0",
    runningSince: Date.now(),
  },
]);

In TimersList just get the values of the useState like this <TimersList timers={timers}/>.