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$(window).on('scroll', function() {
  $('.cd-timeline-block').each(function() {
    if(
      $(this).offset().top <= $(window).scrollTop()+$(window).height()*0.75 &&
      $(this).find('.cd-timeline-img').hasClass('is-hidden')
    ) {
      $(this).find('.cd-timeline-img, .cd-timeline-content').removeClass('is-hidden').addClass('bounce-in');
    }
  });
});

#cd-timeline {
  position: relative;
  padding: 2em 0;
  margin-top: 2em;
  margin-bottom: 2em;
}
#cd-timeline::before {
  /* this is the vertical line */
  content: '';
  position: absolute;
  top: 0;
  height: 100%;
  width: 4px;
  background: #d7e4ed;
  left: 50%;
  margin-left: -2px;
}
.cd-container::after {
  content: '';
  display: table;
  clear: both;
}
.cd-container {
  width: 90%;
  max-width: 1170px;
  margin: 0 auto;
}
.cd-timeline-block:first-child {
  margin-top: 0;
}
.cd-timeline-block {
  position: relative;
      margin: 4em 0;
}
.cd-timeline-content {
  margin-left: 0;
  padding: 1.6em;
  width: 42%;
  position: relative;
  background: white;
  border-radius: 0.25em;
  padding: 1em;
  box-shadow: 0 3px 0 #d7e4ed;
}
.cd-timeline-content .cd-date {
  position: absolute;
  width: 100%;
  left: 122%;
  top: 6px;
  font-size: 16px;
  font-size: 1rem;
}
.cd-timeline-block:nth-child(even) .cd-timeline-content .cd-date {
  left: auto;
  right: 122%;
  text-align: right;
}
.cd-timeline-block:nth-child(even) .cd-timeline-content {
  float: right;
}
.cd-timeline-block:after {
  content: "";
  display: table;
  clear: both;
}
.cd-timeline-img {
  width: 60px;
  height: 60px;
  left: 50%;
  margin-left: -30px;
  -webkit-transform: translateZ(0);
  -webkit-backface-visibility: hidden;
}
.cd-timeline-img {
  position: absolute;
  top: 0;
  border-radius: 50%;
  box-shadow: 0 0 0 4px white, inset 0 2px 0 rgba(0, 0, 0, 0.08), 0 3px 0 4px rgba(0, 0, 0, 0.05);
  background: #105a8b;
}
.cd-timeline-img img,.cd-timeline-img svg {
  display: block;
  width: 24px;
  height: 24px;
  position: relative;
  left: 50%;
  top: 50%;
  margin-left: -12px;
  margin-top: -12px;
  vertical-align: middle;
}
.cssanimations .cd-timeline-img.is-hidden,.cssanimations .cd-timeline-content.is-hidden {
  visibility: hidden;
}
.cssanimations .cd-timeline-img.bounce-in,.cssanimations .cd-timeline-content.bounce-in {
  visibility: visible;
  animation: cd-bounce-1 0.6s;
}
 
@keyframes cd-bounce-1 {
  0% {
    opacity: 0;
    transform: scale(0.5);
  }
 
  60% {
    opacity: 1;
    transform: scale(1.2);
  }
 
  100% {
    transform: scale(1);
  }
}

<!-- main timeline section -->
<section id="cd-timeline" class="cd-container cssanimations">
  <!-- single timeline event -->
  <div class="cd-timeline-block">
    <div class="cd-timeline-img cd-picture">
      <img src="event-calender.png" />
    </div>
    <div class="cd-timeline-content">
      <h2>Event 1</h2>
      <p>Event 1 Description </p>
      <span class="cd-date">Sunday, 19 June 2016</span>
    </div>
  </div>
</section>