class SplitDateTimeField

    def clean(self, value):
        """
        Validate every value in the given list. A value is validated against
        the corresponding Field in self.fields.

        For example, if this MultiValueField was instantiated with
        fields=(DateField(), TimeField()), clean() would call
        DateField.clean(value[0]) and TimeField.clean(value[1]).
        """
        clean_data = []
        errors = []
        if not value or isinstance(value, (list, tuple)):
            if not value or not [v for v in value if v not in self.empty_values]:
                if self.required:
                    raise ValidationError(self.error_messages['required'], code='required')
                else:
                    return self.compress([])
        else:
            raise ValidationError(self.error_messages['invalid'], code='invalid')
        for i, field in enumerate(self.fields):
            try:
                field_value = value[i]
            except IndexError:
                field_value = None
            if field_value in self.empty_values:
                if self.require_all_fields:
                    # Raise a 'required' error if the MultiValueField is
                    # required and any field is empty.
                    if self.required:
                        raise ValidationError(self.error_messages['required'], code='required')
                elif field.required:
                    # Otherwise, add an 'incomplete' error to the list of
                    # collected errors and skip field cleaning, if a required
                    # field is empty.
                    if field.error_messages['incomplete'] not in errors:
                        errors.append(field.error_messages['incomplete'])
                    continue
            try:
                clean_data.append(field.clean(field_value))
            except ValidationError as e:
                # Collect all validation errors in a single list, which we'll
                # raise at the end of clean(), rather than raising a single
                # exception for the first error we encounter. Skip duplicates.
                errors.extend(m for m in e.error_list if m not in errors)
        if errors:
            raise ValidationError(errors)

        out = self.compress(clean_data)
        self.validate(out)
        self.run_validators(out)
        return out

    def clean(self, value):
        """
        Validate the given value and return its "cleaned" value as an
        appropriate Python object. Raise ValidationError for any errors.
        """
        value = self.to_python(value)
        self.validate(value)
        self.run_validators(value)
        return value

    def compress(self, data_list):
        if data_list:
            # Raise a validation error if time or date is empty
            # (possible if SplitDateTimeField has required=False).
            if data_list[0] in self.empty_values:
                raise ValidationError(self.error_messages['invalid_date'], code='invalid_date')
            if data_list[1] in self.empty_values:
                raise ValidationError(self.error_messages['invalid_time'], code='invalid_time')
            result = datetime.datetime.combine(*data_list)
            return from_current_timezone(result)
        return None

    def compress(self, data_list):
        """
        Return a single value for the given list of values. The values can be
        assumed to be valid.

        For example, if this MultiValueField was instantiated with
        fields=(DateField(), TimeField()), this might return a datetime
        object created by combining the date and time in data_list.
        """
        raise NotImplementedError('Subclasses must implement this method.')

    def has_changed(self, initial, data):
        if self.disabled:
            return False
        if initial is None:
            initial = ['' for x in range(0, len(data))]
        else:
            if not isinstance(initial, list):
                initial = self.widget.decompress(initial)
        for field, initial, data in zip(self.fields, initial, data):
            try:
                initial = field.to_python(initial)
            except ValidationError:
                return True
            if field.has_changed(initial, data):
                return True
        return False

    def has_changed(self, initial, data):
        """Return True if data differs from initial."""
        # Always return False if the field is disabled since self.bound_data
        # always uses the initial value in this case.
        if self.disabled:
            return False
        try:
            data = self.to_python(data)
            if hasattr(self, '_coerce'):
                return self._coerce(data) != self._coerce(initial)
        except ValidationError:
            return True
        # For purposes of seeing whether something has changed, None is
        # the same as an empty string, if the data or initial value we get
        # is None, replace it with ''.
        initial_value = initial if initial is not None else ''
        data_value = data if data is not None else ''
        return initial_value != data_value

    def validate(self, value):
        pass

    def validate(self, value):
        if value in self.empty_values and self.required:
            raise ValidationError(self.error_messages['required'], code='required')