title: DateField 'str' object has no attribute 'year'
body: <p>When trying to access the year and month attributes of my <code>DateField</code> objects I am getting the error </p>
  
  <blockquote>
    <p>AttributeError: 'str' object has no attribute 'date'.</p>
  </blockquote>
  
  <p>I thought that DateField objects were saved as Python Datetime objects instead of strings.</p>
  
  <p>Here is the models.py:</p>
  
  <pre><code>class MonthControlRecord(models.Model):
      STATUS_CHOICES = (
          (0, 'Open'),
          (1, 'Locked'),
          (2, 'Closed'),
      )
      employee = models.ForeignKey(Employee, on_delete=models.CASCADE)
      first_day_of_month = models.DateField()
      status = models.IntegerField(choices=STATUS_CHOICES, default=0)
  
      @property
      def get_year_month(self):
          return self.first_day_of_month.year, self.first_day_of_month.month
  
      def __str__(self):
          return self.employee, self.first_day_of_month
  </code></pre>
  
  <p>and the tests.py:</p>
  
  <pre><code>employee = Employee.objects.get(staff_number="0001")
  mcr = MonthControlRecord(employee=employee, first_day_of_month="2015-12-01")
  mcrYearMonth = mcr.get_year_month
  </code></pre>
  
  <p>and the error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/Users/James/Django/MITS/src/timesheet/tests.py", line 87, in test_new_month_control_record
      mcrYearMonth = mcr.get_year_month
    File "/Users/James/Django/MITS/src/timesheet/models.py", line 54, in get_year_month
      return self.first_day_of_month.year, self.first_day_of_month.month
  AttributeError: 'str' object has no attribute 'year'
  </code></pre>