code: function(strId) {
          var idx = -1,
              li = strId.lastIndexOf("_cell");
  
          if (li > -1) {
              idx = parseInt(strId.substring(li + 5), 10);
          }
  
          return idx;
      }
docs: Given the id used to mark each Calendar cell, this method
  extracts the index number from the id.
  
  @param {String} strId The cell id
  @return {Number} The index of the cell, or -1 if id does not contain an index number