django ORM queryset group by month, week, TruncMonth

How to group by queryset on datetime field in Django ORM?

models:

class test1(models.Model):
    id = models.AutoField(primary_key=True, unique=True, verbose_name='id')
    name = models.CharField(verbose_name='name', max_length=200)
    cdate = models.DateField(verbose_name='date', default=timezone.now)

queryset data

for i in test1.objects.all(): 
    print i.id, i.name, i.cdate

2 a 2017-08-11
3 b 2017-08-11
4 c 2017-08-11
5 a 2017-08-11
6 a 2017-08-11

need group by month and count IDs with Django orm.

queryset

data = test1.objects.annotate(month=TruncMonth('cdate')).values('month').annotate(c=Count('id'))
for i in data:
    print i

result

{'c': 1, 'month': datetime.date(2017, 8, 1)}
{'c': 1, 'month': datetime.date(2017, 8, 1)}
{'c': 1, 'month': datetime.date(2017, 8, 1)}
{'c': 1, 'month': datetime.date(2017, 8, 1)}
{'c': 1, 'month': datetime.date(2017, 8, 1)}

why not?

{'c': 5, 'month': datetime.date(2017, 8, 1)}