   <li><a href="dart-core/UnsupportedError-class.html">UnsupportedError</a></li>
    </ol>
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      <div><h1>Duration class </h1></div>

    <section class="desc markdown">
      <p>A span of time, such as 27 days, 4 hours, 12 minutes, and 3 seconds.</p>
<p>A <code>Duration</code> represents a difference from one point in time to another. The
duration may be "negative" if the difference is from a later time to an
earli