def crontab_to_schedule(c):
        """Return string representation of CrontabSchedule model"""
        def s(f):
            return f and str(f).replace(' ', '') or '*'

        return '%s %s %s %s %s' % (s(c.minute), s(c.hour), s(c.day_of_month), s(c.month_of_year), s(c.day_of_week))