JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="events-list-wrapper">
  <div class="event">
    <p class="date" data-date="21-01-2017"><span>Jan</span> 17-21</p>
    <h3>Event Title</h3> ...
  </div>
  <div class="event">
    <p class="date" data-date="29-08-2017"><span>Aug</span> 29</p>
    <h3>Event Title</h3> ...
  </div>
  <div class="event">
    <p class="date" data-date="12-09-2017"><span>Sept</span> 10-12</p>
    <h3>Event Title</h3> ...
  </div>
</div>

CSS

.past {
  border: 1px solid gray;
}

.today {
  border: 1px solid blue;
}

JavaScript

let today = Date.now()

$('div.event').each(function() {

  let div = $(this);
  let divDate = Date.parse($(data-date, this).text());

  if (divDate < today) {
    div.addClass('past');
  } else {
    div.addClass('today');
  }

});