Add class to a multiple/specific day in bootstrap datepicker?

Depending on the datepicker you are using you can do something like this:

Most of the date pickers have a beforeShowDay option. You can set a class here to add to the day you want to change.

For this example im using http://eternicode.github.io/bootstrap-datepicker

An example of how to do this can be found here: jsFiddle

You will want to put the dates you want to highlight / mark into an array:

var active_dates = ["23/5/2014","21/5/2014"];

Then use the beforeShowDay option to check the dates against the current day being shown and then apply a class.

<input type="text" id="datepicker" />

$("#datepicker").datepicker({
     format: "dd/mm/yyyy",
     autoclose: true,
     todayHighlight: true,
     beforeShowDay: function(date){
         var d = date;
         var curr_date = d.getDate();
         var curr_month = d.getMonth() + 1; //Months are zero based
         var curr_year = d.getFullYear();
         var formattedDate = curr_date + "/" + curr_month + "/" + curr_year

         if ($.inArray(formattedDate, active_dates) != -1){
           return {
              classes: 'activeClass'
           };
         }
      return;
  }

});`

The activeClass can be any form of CSS. In my example i have just changed the background color. In your example you could offset an image and apply it to the day.

.activeClass{
    background: #F00; 
  }