title: Filter people from Django model using birth date
body: <p>I have this model:</p>
  
  <pre><code>class People(models.Model):
      """
      People model
      """
      name = models.CharField(max_length=120)
      birth_date = models.DateField()
  </code></pre>
  
  <p>and I want to filter all people with an age given as parameter, example:</p>
  
  <pre><code>min_age = 24
  # Filter people older than  ´min_age´
  people = People.objects.filter(birth_date__lte = (#something here to filter with age))
  </code></pre>
  
  <p>How can I do that?</p>