select_datetime

# File actionpack/lib/action_view/helpers/date_helper.rb, line 649
      def select_datetime
        order = date_order.dup
        order -= [:hour, :minute, :second]
        @options[:discard_year]   ||= true unless order.include?(:year)
        @options[:discard_month]  ||= true unless order.include?(:month)
        @options[:discard_day]    ||= true if @options[:discard_month] || !order.include?(:day)
        @options[:discard_minute] ||= true if @options[:discard_hour]
        @options[:discard_second] ||= true unless @options[:include_seconds] && !@options[:discard_minute]

        # If the day is hidden and the month is visible, the day should be set to the 1st so all month choices are
        # valid (otherwise it could be 31 and February wouldn't be a valid date)
        if @datetime && @options[:discard_day] && !@options[:discard_month]
          @datetime = @datetime.change(:day => 1)
        end

        if @options[:tag] && @options[:ignore_date]
          select_time
        else
          [:day, :month, :year].each { |o| order.unshift(o) unless order.include?(o) }
          order += [:hour, :minute, :second] unless @options[:discard_hour]

          build_selects_from_types(order)
        end
      end