    # File lib/action_view/helpers/date_helper.rb, line 415
          def select_hour(datetime, options = {}, html_options = {})
            val = datetime ? (datetime.kind_of?(Fixnum) ? datetime : datetime.hour) : ''
            if options[:use_hidden]
              hidden_html(options[:field_name] || 'hour', val, options)
            else
              hour_options = []
              0.upto(23) do |hour|
                hour_options << ((val == hour) ?
                  content_tag(:option, leading_zero_on_single_digits(hour), :value => leading_zero_on_single_digits(hour), :selected => "selected") :
                  content_tag(:option, leading_zero_on_single_digits(hour), :value => leading_zero_on_single_digits(hour))
                )
                hour_options << "\n"
              end
              select_html(options[:field_name] || 'hour', hour_options.join, options, html_options)
            end
          end