I have a countdown until New Year, now I want to have other countdowns until Easter for example. I thought about making other constants like "difference" but then I don't know how to make that other stuff down there to change depending on which subject that is chosen.

import './App.css';
import React, {useEffect, useState} from "react";

function App() {
  const calculateTimeLeft = () => {
    let year = new Date().getFullYear();

    const difference = +new Date(`01/01/${year+1}`) - +new Date();

    let timeLeft = {};

    if (difference > 0) {
      timeLeft = {
        days: Math.floor(difference / (1000 * 60 * 60 * 24)),
        hours: Math.floor((difference / (1000 * 60 * 60)) % 24), 
        minutes: Math.floor((difference / 1000 / 60) % 60),
        seconds: Math.floor((difference / 1000) % 60)
      };
    }

    return timeLeft
  };
    
    const [timeLeft, setTimeLeft] = useState(calculateTimeLeft());
    const [year] = useState(new Date().getFullYear());

    useEffect(() => {
      const timer = setTimeout(() => {
        setTimeLeft(calculateTimeLeft());
      }, 1000);
      return () => clearTimeout(timer);
    });
    const timerComponents = [];

  Object.keys(timeLeft).forEach((interval) => {
    if (!timeLeft[interval]) {
      return;
  }

  timerComponents.push(
    <span>
      {timeLeft[interval]} {interval}{" "}
    </span>
  );
  });
  return (
    <div className="App">
      <h1>New Year {year+1} Countdown</h1>
      {timerComponents.length ? timerComponents : <span>Time's up!</span>}
    </div>
  );
  };

export default App;