title: How to properly use ThreeTenABP to get the time in milliseconds between two dates based on UTC
body: <p>I'm using this library I just discovered which is supposedly less heavier than Joda time for android and I said what the heck, let's use it. But now I'm struggling to find any good examples on the web about how to use it, besides these two methods I have: </p>
  
  <pre><code>// ZonedDateTime contains timezone information at the end
  // For example, 2011-12-03T10:15:30+01:00[Europe/Paris]
  public static ZonedDateTime getDate(String dateString) {
      return ZonedDateTime.parse(dateString).withZoneSameInstant(ZoneId.of("UTC"));
  }
  
  public static String formatDate(String format, String dateString) {
      return DateTimeFormatter.ofPattern(format).format(getDate(dateString));
  }
  </code></pre>
  
  <p>So how can I get the difference between two dates with this library?</p>