python - strptime検証エラーdjango

Question

ユーザーが日付を設定する日付範囲ピッカーがあります。フォーマットの選択は「DD MMM YYYY」で、私が使用しているものに合わせます

    datetime.datetime.strptime(time, "%d %b %Y");

それでもエラーが発生します

    Exception Value:[u"'01 Aug 2013' value has an invalid date format. It must be in   YYYY-MM-DD format."]

何がうまくいかないのでしょうか？しばらくこれに固執しました。

    def form_valid(self, form):
      new_obj = form.save(commit=False)
      new_obj.date_pickup_from, new_obj.date_pickup_to = form.cleaned_data['pickup_daterange'].split(' to ')
      new_obj.date_delivery_from, new_obj.date_delivery_to = form.cleaned_data['delivery_daterange'].split(' to ')

ここにフォームがあります

pickup_daterange = forms.CharField(
    label=_('Pickup Within'),
    widget=forms.TextInput(attrs={'class': 'daterange'}),
    validators=[
        RegexValidator(
            regex=r'\d{2}\ \w{3}\ \d{4}\ to\ \d{2}\ \w{3}\ \d{4}',
            message=_(u'Range must be of format "mm/dd/yyyy to mm/dd/yyyy"'),
            code='invalid_range'
        )
    ],
    help_text=_('Within what dates do you want the pickup?')
)
delivery_daterange = forms.CharField(
    label=_('Delivery Within'),
    widget=forms.TextInput(attrs={'class': 'daterange'}),
    validators=[
        RegexValidator(
            regex=r'\d{2}\ \w{3}\ \d{4}\ to\ \d{2}\ \w{3}\ \d{4}',
            message=_(u'Range must be of format "mm/dd/yyyy to mm/dd/yyyy"'),
            code='invalid_range'
        )
    ],
    help_text=_('Within what dates do you want the delivery?')
)

models.py

date_delivery_from = models.DateField(_('Date of Delivery From'), blank=True, null=True)
date_delivery_to = models.DateField(_('Date of Delivery To'), blank=True, null=True)

strptimeを呼び出しているフォームクラスの関数

    def clean_delivery_daterange(self):
      daterange_pattern = re.compile(r'(\d{2}\ \w{3}\ \d{4})\ to\ (\d{2}\ \w{3}\ \d{4})')
      delivery_daterange = self.cleaned_data['delivery_daterange']
      pickup_daterange = self.cleaned_data['pickup_daterange']

      str_pickup_from, str_pickup_to = daterange_pattern.search(pickup_daterange).groups()
      str_delivery_from, str_delivery_to = daterange_pattern.search(delivery_daterange).groups()

      delivery_from = datetime.datetime.strptime(str_delivery_from, "%d %b %Y")
      pickup_from = datetime.datetime.strptime(str_pickup_from, "%d %b %Y")
      if delivery_from < pickup_from:
        raise forms.ValidationError('Delivery dates cannot be before pickup dates')
      return delivery_daterange