def _increment_field_value(self, dateval, fieldnum):
        """
        Increments the designated field and resets all less significant fields to their minimum
        values.

        :type dateval: datetime
        :type fieldnum: int
        :return: a tuple containing the new date, and the number of the field that was actually
            incremented
        :rtype: tuple
        """

        values = {}
        i = 0
        while i < len(self.fields):
            field = self.fields[i]
            if not field.REAL:
                if i == fieldnum:
                    fieldnum -= 1
                    i -= 1
                else:
                    i += 1
                continue

            if i < fieldnum:
                values[field.name] = field.get_value(dateval)
                i += 1
            elif i > fieldnum:
                values[field.name] = field.get_min(dateval)
                i += 1
            else:
                value = field.get_value(dateval)
                maxval = field.get_max(dateval)
                if value == maxval:
                    fieldnum -= 1
                    i -= 1
                else:
                    values[field.name] = value + 1
                    i += 1

        difference = dateval.replace(tzinfo=None) - datetime(**values)
        return self.timezone.normalize(dateval + difference), fieldnum
dataset/ETHPy150Open agronholm/apscheduler/apscheduler/triggers/cron/__init__.py/CronTrigger._increment_field_value/swapped operands of `-`