Simple Digital Clock

<time id="realtime"></time>

body {
    min-height: 100%;
    margin: 0;
    background: rgb(0,122,255);
    color: #fff;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex;
    -webkit-align-items: center;
    -ms-flex-align: center;
    align-items: center;
    -webkit-justify-content: center;
    -ms-flex-pack: center;
    justify-content: center;
}

#realtime {
    font-family: Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;
    font-weight: 100;
    display: block;
    text-align: center;
    font-size: 12vw;
    padding: 4rem 0;
}

#realtime span {
    display: inline-block;
    font-family: Avenir Next, Nunito, sans-serif;
    font-weight: 100;
    font-size: 8vw;
    position: relative;
    top: -2vw;
}

@media all and (max-width: 600px) {
    #realtime {
        font-size: 4rem;
        padding: 2rem 0;
    };
}

@media all and (max-width: 350px) {
 
    #realtime {
        font-size: 3rem;
        padding: 2rem 0;
    };
}

<script type='text/javascript'>
var currentTime = document.getElementById("realtime");
function zeropadder(n) {
  return (parseInt(n,10) < 10 ? '0' : '')+n;
}
function updateTime(){
  var timeNow= new Date(),
  hh = timeNow.getHours(),
  mm = timeNow.getMinutes(),
  ss = timeNow.getSeconds(),
  formatAMPM = (hh >= 12?'PM':'AM');
  hh = hh % 12 || 12;
  currentTime.innerHTML = hh + "<span>:</span>" + zeropadder(mm) + "<span>:</span>" + zeropadder(ss) + " " + formatAMPM;
  setTimeout(updateTime,1000);
}
updateTime();
</script>

Result