  
  We'll be using the following model in examples of each function::
  
      class Experiment(models.Model):
          start_time = models.DateTimeField()
          start_date = models.DateField(null=True, blank=True)
          end_time = models.DateTimeField(null=True, blank=True)
          end_date = models.DateField(null=True, blank=True)
  
  ``Extract``
 
</s> remove         end_time = models.DateTimeField(null=True, blank=True)
 </s> add         end_datetime = models.DateTimeField(null=True, blank=True) </s> remove     ...    start_time=start, start_date=start.date(),
    ...    end_time=end, end_date=end.date())
 </s> add     ...    start_datetime=start, start_date=start.date(),
    ...    end_datetime=end, end_date=end.date()) </s> remove     ...    start_year=Extract('start_time', 'year')).get()
 </s> add     ...    start_year=Extract('start_datetime', 'year')).get() </s> remove     ...    month=TruncMonth('start_time', tzinfo=melb)).values('month').annotate(
 </s> add     ...    month=TruncMonth('start_datetime', tzinfo=melb)).values('month').annotate( </s> remove     >>> Experiment.objects.create(start_time=start1, start_date=start1.date())
    >>> Experiment.objects.create(start_time=start2, start_date=start2.date())
    >>> Experiment.objects.create(start_time=start3, start_date=start3.date())
 </s> add     >>> Experiment.objects.create(start_datetime=start1, start_date=start1.date())
    >>> Experiment.objects.create(start_datetime=start2, start_date=start2.date())
    >>> Experiment.objects.create(start_datetime=start3, start_date=start3.date())
        start_datetime = models.DateTimeField()
  
  We'll be using the following model in examples of each function::
  
      class Experiment(models.Model):
        start_datetime = models.DateTimeField()
          start_date = models.DateField(null=True, blank=True)
          end_time = models.DateTimeField(null=True, blank=True)
          end_date = models.DateField(null=True, blank=True)
  
  ``Extract``
keep keep keep keep replace keep keep keep keep keep
 Refs #25774 -- Adjusted datetime database function docs field names. 
docs/ref/models/database-functions.txt