title: How to get the Modelfield - datetime.now
body: <p>i've been strugling a lot with arithmetics on Dates. First of all i got the date between two datetimeFields (models) and thats ok. but i'd like to get the (To_do.end)-datetime.now()</p>
  
  <p>i've got the 2 datefields difference by the :<br>
  To_do.objects.annotate(
                       delta=ExpressionWrapper(F('end') - F('start'), output_field=DurationField())</p>
  
  <p>since i've been trying the same with a variable=datetime.now() and still don't get it</p>
  
  <p>thats the test that im trying to get the succes</p>
  
  <pre><code>def index(request):
      myDate = datetime.now()
      days_left1 = To_do.objects.annotate(
          delta=ExpressionWrapper(F('end') - myDate, output_field=DurationField()))
      return render(request, 'ongoingtest.html', {
          'myDate': myDate,
          'days_left1': days_left1,
      })
  
  </code></pre>
  
  <p>thats what i did to get the difference between the two model fields</p>
  
  <pre><code>class HomeView(ListView):
      template_name = 'ongoing.html'
      model = To_do
  
      def get_queryset(self):
          return To_do.objects.annotate(
              delta=ExpressionWrapper(F('end') - F('start'), output_field=DurationField())
          )
  </code></pre>
  
  <p>models.py:</p>
  
  <pre><code>class To_do (models.Model):
      task = models.CharField(max_length=150)
      topic = models.CharField(max_length=150)
      how = models.TextField(max_length=600)
      start = models.DateTimeField(auto_now_add=True)
      end = models.DateTimeField(blank=False)
      updated_at = models.DateTimeField(auto_now=True)
  
      def __str__(self):
          return self.task
  </code></pre>
  
  <p>just get the  To_do.end - datetime.now()</p>