title: django form not validating the datefield
body: <p>I have a form :</p>
  
  <pre><code>class AppointmentForm1(forms.Form):
  
  f_name = forms.CharField(max_length=100)
  appointment_date = forms.DateField()
  
  def clean_appointment_date(self):
      appointment_date = self.cleaned_data['appointment_date']
      today = date.today()
      next_week = today + timedelta(days=7)
      if appointment_date is None:
          raise forms.ValidationError("You must provide a date to take appointment")
      if appointment_date &lt; today:
          raise forms.ValidationError("You cannot take appointment on past date")
      if appointment_date &gt; next_week:
          raise forms.ValidationError("You can only take appointment with in one week")
      return appointment_date
  </code></pre>
  
  <p>and I have catched the appointment_date in view..</p>
  
  <pre><code>appointment_date = request.GET.get('appointment_date')
  app = DoctorAppointment()
  app.appointment_date = appointment_date
  app.save()
  </code></pre>
  
  <p>I have model named DoctorAppointment.
  When I do this and enter whatever value for appointment_date it saves in the database. It doesn't show any error. </p>
  
  <p>In my template I have done:</p>
  
  <pre><code>{{ form.appointment_date.errors }}
  {{ appointment_form.appointment_date }}
  </code></pre>
  
  <p>Am I doing anything wrong for validating the datefield. The values for <code>today = date.today()
          next_week = today + timedelta(days=7)</code> are correct I have printed in the console.</p>
  
  <p>My database for appointment_date is:</p>
  
  <pre><code>appointment_date = models.DateField()
  </code></pre>
  
  <p>Need help??
  Thanks in advance..</p>