title: How should I use DurationField in my model?
body: <p>In my model I want to be able to input duration, like <em>2 years</em>, <em>5 months</em>, etc.</p>
  <p>In version 1.8 DurationField was introduced so I tried using that:</p>
  <p>In my model I have</p>
  <pre><code>user_validPeriod = models.DurationField()
  </code></pre>
  <p>Trying to add a new <em>User</em> from my admin panel, If I try typing something like <em>2d</em> or <em>2 days</em> in the appearing text-field though I get <code>Enter a valid duration</code>.</p>
  <p><img src="https://i.stack.imgur.com/VszE6.png" alt="enter image description here" /></p>
  <p>Can someone provide me with an example of how this field is supposed to be used?</p>