index.html.erb

<table>
  <% @parties.weeks.each do |week| %>
    <tr>
      <% week.days.each do |day| %>
        <td>
          <ul>
            <% day.each do |party| %>
              <li><!-- party info here --></li>
            <% end %>
          </ul>
        </td>
      <% end %>
    </tr>
  <% end %>
</table>

parties_controller.rb

class PartiesController < ApplicationController
  def index
    @parties = Party.within(:month => params[:date])
  end
end