How can i stop countdown after zero

Question

const second = 1000,
  minute = second * 60,
  hour = minute * 60,
  day = hour * 24;

let countDown = new Date('February 03, 2021 12:10:00').getTime(),
  x = setInterval(function() {

    let now = new Date().getTime(),
      distance = countDown - now;
    var hours = Math.floor((distance % (day)) / (hour));
    var days = Math.floor(distance / (day));
    var minutes = Math.floor((distance % (hour)) / (minute));
    var seconds = Math.floor((distance % (minute)) / second);
    
    document.getElementById('days').innerText = (days < 10) ? '0' + days : days,
      document.getElementById('hours').innerText = (hours < 10) ? '0' + hours : hours,
      document.getElementById('minutes').innerText = (minutes < 10) ? '0' + minutes : minutes,
      document.getElementById('seconds').innerText = (seconds < 10) ? '0' + seconds : seconds;
      
  }, second)
  
if (second < 10 && minute < 10 && hour < 10 && day < 10) {
  countDown = "0" + countDown;
}

#timer {
  list-style-type: none;
  justify-content: center;
  display: flex;
}

#timer>li {
  float: left;
  font-size: 50px;
  padding: 0px 20px;
  font-weight: bold;
}

.timer_text {
  font-size: 15px;
  text-align: center;
}

<p style="text-align:center;text-transform:uppercase;font-weight:bold; font-size:25px;">Count down</p>

<ul id="timer">
  <li class="clock_li"><span id="days"></span>
    <p class="timer_text">DAYS</p>
  </li>
  <li>:</li>
  <li class="clock_li"><span id="hours"></span>
    <p class="timer_text">HOURS</p>
  </li>
  <li>:</li>
  <li class="clock_li"><span id="minutes"></span>
    <p class="timer_text">MINUTES</p>
  </li>
  <li>:</li>
  <li class="clock_li"><span id="seconds"></span>
    <p class="timer_text">SECONDS</p>
  </li>
</ul>

Hi guys! i want this countdown is stop and display 0 in each part (day, hour, min, sec) after zero but as you can see in the code, now it display as "0-(time)". what should i add in my script to make it stop and show "00" in each part after timeout?

so as a result, i want to make it 00:00:00:00 after timeout :) any help will be so appreciated thanks! :)