_('Enter a valid date in YYYY-MM-DD format.'))
forms.DateField input_formats 这样的论点:
forms.DateField
input_formats
class MyForm(forms.Form): start_date = forms.DateField(input_formats=['%d/%m/%Y'])
看 http://docs.djangoproject.com/en/dev/ref/forms/fields/#datefield
https://docs.djangoproject.com/en/dev/ref/models/instances/?from=olddocs#what-happens-when-you-save