def build_day_rules(rule, expression)
      rule = rule.day_of_month(*expression.day_of_month) unless expression.day_of_month.blank?

      rule
    end
def build_day_rules(rule, expression)
      rule = rule.day_of_month(*expression.day_of_month) unless expression.day_of_month.blank?

      rule
    end
:nodoc: