title: django.core.exceptions.FieldError: Cannot resolve keyword 'timestamp' into field
body: <p>Welcome friends, </p>
  
  <p>Unfortunately I have FieldError. Please help</p>
  
  <p>Environment:</p>
  
  <pre><code>Django Version: 1.10.6
  Python Version: 3.5.2
  </code></pre>
  
  <p>utils.py</p>
  
  <pre><code>import datetime
  from django.utils import timezone
  from django.contrib.contenttypes.models import ContentType
  from .models import Action
  
  def create_action(user, verb, target=None):
      now = timezone.now()
      last_minute = now - datetime.timedelta(seconds=60)
      similar_actions = Action.objects.filter(user_id=user.id, verb=verb, timestamp__gte=last_minute)
      if target:
          target_ct = ContentType.objects.get_for_model(target)
          similar_actions = similar_actions.filter(
                                           target_ct=target_ct,
                                           target_id=target.id)
      if not similar_actions:
          # Nie znaleziono żadnych akcji.
          action = Action(user=user, verb=verb, target=target)
          action.save()
          return True
      return False
  </code></pre>
  
  <p>models.py</p>
  
  <pre><code>from django.db import models
  from django.contrib.auth.models import User
  from django.contrib.contenttypes.models import ContentType
  from django.contrib.contenttypes.fields import GenericForeignKey
  
  class Action(models.Model):
     user = models.ForeignKey(User,
                           related_name='actions',
                           db_index=True)
     verb = models.CharField(max_length=255)
  
     target_ct = models.ForeignKey(ContentType,
                                blank=True,
                                null=True,
                                related_name='target_obj')
     target_id = models.PositiveIntegerField(null=True,
                                          blank=True,
                                          db_index=True)
     target = GenericForeignKey('target_ct', 'target_id')
     created = models.DateTimeField(auto_now_add=True,
                                 db_index=True)
  
     class Meta:
         ordering = ('-created',)
  </code></pre>
  
  <p>I received this error traceback from the Django Shell:</p>
  
  <pre><code> django.core.exceptions.FieldError: Cannot resolve keyword 'timestamp' 
   into field. Choices are: created, id, target, target_ct, 
   target_ct_id, target_id, user, user_id, verb
  [23/Mar/2017 17:20:46] "POST /account/users/follow/ HTTP/1.1" 500 18933
  </code></pre>
  
  <p>I received this error from browser console:</p>
  
  <pre><code>POST http://127.0.0.1:8000/account/users/follow/ 500 (Internal Server Error)
  </code></pre>
  
  <p>Does anyone coped with this?</p>
  
  <p>Does anyone have any advise for this?</p>