build_selects_from_types

# File actionview/lib/action_view/helpers/date_helper.rb, line 1137
        def build_selects_from_types(order)
          select = +""
          first_visible = order.find { |type| !@options[:"discard_#{type}"] }
          order.reverse_each do |type|
            separator = separator(type) unless type == first_visible # don't add before first visible field
            select.insert(0, separator.to_s + public_send("select_#{type}").to_s)
          end
          select.html_safe
        end