def clean_start_datetime(self):
        start = self.cleaned_data['start_datetime']
        # Day entry can't start before the targeted day date
        if start and start.date() < self.daydate:
            raise forms.ValidationError(_("You can't start a day before itself"))
        # Day entry can't start after the targeted day date
        if start and start.date() > self.daydate:
            raise forms.ValidationError(_("You can't start a day after itself"))