Countdown Timer | Countdown Timer Html Css Javascript

 <div class="container">  
  <h1 id="headline">Countdown to my birthday</h1>  
  <div id="countdown">  
   <ul>  
    <li><span id="days"></span>days</li>  
    <li><span id="hours"></span>Hours</li>  
    <li><span id="minutes"></span>Minutes</li>  
    <li><span id="seconds"></span>Seconds</li>  
   </ul>  
  </div>  
  <div id="content" class="emoji">  
   <span>🥳</span>  
   <span>🎉</span>  
   <span>🎂</span>  
  </div>  
 </div>  

There is all the HTML code for the Countdown Timer. Now, you can see an output with a Countdown Timer then we write javascript for the Countdown Timer.

 /* general styling */  
 :root {  
  --smaller: .75;  
 }  
 * {  
  box-sizing: border-box;  
  margin: 0;  
  padding: 0;  
 }  
 html, body {  
  height: 100%;  
  margin: 0;  
 }  
 body {  
  align-items: center;  
  background-color: #ffd54f;  
  display: flex;  
  font-family: -apple-system,   
   BlinkMacSystemFont,   
   "Segoe UI",   
   Roboto,   
   Oxygen-Sans,   
   Ubuntu,   
   Cantarell,   
   "Helvetica Neue",   
   sans-serif;  
 }  
 .container {  
  color: #333;  
  margin: 0 auto;  
  text-align: center;  
 }  
 h1 {  
  font-weight: normal;  
  letter-spacing: .125rem;  
  text-transform: uppercase;  
 }  
 li {  
  display: inline-block;  
  font-size: 1.5em;  
  list-style-type: none;  
  padding: 1em;  
  text-transform: uppercase;  
 }  
 li span {  
  display: block;  
  font-size: 4.5rem;  
 }  
 .emoji {  
  display: none;  
  padding: 1rem;  
 }  
 .emoji span {  
  font-size: 4rem;  
  padding: 0 .5rem;  
 }  
 @media all and (max-width: 768px) {  
  h1 {  
   font-size: calc(1.5rem * var(--smaller));  
  }  
  li {  
   font-size: calc(1.125rem * var(--smaller));  
  }  
  li span {  
   font-size: calc(3.375rem * var(--smaller));  
  }  
 }  

Css Updated output

 (function () {  
  const second = 1000,  
     minute = second * 60,  
     hour = minute * 60,  
     day = hour * 24;  
  //I'm adding this section so I don't have to keep updating this pen every year :-)  
  //remove this if you don't need it  
  let today = new Date(),  
    dd = String(today.getDate()).padStart(2, "0"),  
    mm = String(today.getMonth() + 1).padStart(2, "0"),  
    yyyy = today.getFullYear(),  
    nextYear = yyyy + 1,  
    dayMonth = "05/29/",  
    birthday = dayMonth + yyyy;  
  today = mm + "/" + dd + "/" + yyyy;  
  if (today > birthday) {  
   birthday = dayMonth + nextYear;  
  }  
  //end  
  const countDown = new Date(birthday).getTime(),  
    x = setInterval(function() {    
     const now = new Date().getTime(),  
        distance = countDown - now;  
     document.getElementById("days").innerText = Math.floor(distance / (day)),  
      document.getElementById("hours").innerText = Math.floor((distance % (day)) / (hour)),  
      document.getElementById("minutes").innerText = Math.floor((distance % (hour)) / (minute)),  
      document.getElementById("seconds").innerText = Math.floor((distance % (minute)) / second);  
     //do something later when date is reached  
     if (distance < 0) {  
      document.getElementById("headline").innerText = "It's my birthday!";  
      document.getElementById("countdown").style.display = "none";  
      document.getElementById("content").style.display = "block";  
      clearInterval(x);  
     }  
     //seconds  
    }, 0)  
  }());  

Final output