anchor.diff:  
           var newDate = ev.newSelection[0];
           var date = dtdate.format(newDate);
  -        var input = $("<input>", { type: "hidden", name: "date", value: date });
  -        $("#reply_form").find("#request_text").append($(input));
  -        $("#reply_form").show()
  +        var day = date.slice(-2);
  +        var day_selector = +day;
  +        if ($("td[id$='_" + day_selector + "']:not(.yui3-calendar-column-hidden)").hasClass("available")) {
  +          var input = $("<input>", { type: "hidden", name: "date", value: date });
  +          $("#reply_form").find("#request_text").append($(input));
  +          $("#reply_form").show()
  +        };
         });
       });
     });
  
positive.code: 
        var dtdate = Y.DataType.Date;
  
        var divLength = $("#available p").length
        for (var i = 0; i < divLength; i++) {
          var availableDay = $("#available p")[i].id
          if (availableDay[0] === "0") {
            availableDay = availableDay[1];
          }
          availableDay = "_" + availableDay;
          $("td[id$='" + availableDay + "']:not(.yui3-calendar-column-hidden)").addClass("available").css("background-color", "#14A714")
        }
  
        calendar.on("selectionChange", function (ev) {
          var newDate = ev.newSelection[0];
  
negative.code:       <div class="col-md-3">
          <div id="available">
            <% @residence.availabilities.each do |availability| %>
              <% if availability.booked == false %>
                <p id="<%= availability.date[-2..-1] %>"><%= availability.id %></p>
              <% end %>
            <% end %>
          </div>
          <div id="booked">
            <% @residence.availabilities.each do |availability| %>
              <% if availability.booked %>
                <p id="<%= availability.date[-2..-1] %>"><%= availability.id %></p>
              <% end %>
            <% end %>
          </div>
        </div>
  