title: change Datetime format django rest framework
body: <p>I want to change date time format in django rest framework</p>
  
  <p>I have implement one logic but it's not fullfill my requirement</p>
  
  <p>Model </p>
  
  <pre><code>class User (models.Model):
      user_id = models.AutoField(primary_key=True)
      user_name = models.CharField(max_length=150)
      created_at = models.DateTimeField()
  </code></pre>
  
  <p>setting.py file I have define the datetime format</p>
  
  <pre><code>REST_FRAMEWORK = {
  
      'DATETIME_FORMAT': "%m/%d/%Y %H:%M:%S",
  }
  </code></pre>
  
  <p>Query </p>
  
  <pre><code>data = User.objects.filter(pk=51)
  serializer = UserSerializer(data, many=True)
  </code></pre>
  
  <p>result after serializer data</p>
  
  <pre><code> {
        "user_id": 41406,
        "user_name": "abc@gmail.com",
        "created_at": "09/26/2016 22:52:16",
   }
  </code></pre>
  
  <p>Now when I hit another model then datetime format is also same like this "09/26/2016 22:52:16" but i do not want this date format in anthor model. </p>
  
  <p>Please let me know if we can change in particular Model datetime format and call it in serializer </p>