code: function(inst, calendar, renderer) {
  			var firstDay = inst.options.firstDay;
  			firstDay = (firstDay == null ? calendar.local.firstDay : firstDay);
  			var header = '';
  			for (var day = 0; day < calendar.daysInWeek(); day++) {
  				var dow = (day + firstDay) % calendar.daysInWeek();
  				header += this._prepare(renderer.dayHeader, inst).replace(/\{day\}/g,
  					'<span class="' + this._curDoWClass + dow + '" title="' +
  					calendar.local.dayNames[dow] + '">' + calendar.local.dayNamesMin[dow] + '</span>');
  			}
  			return header;
  		}
docs: Generate the HTML for the day headers.
  @memberof CalendarsPicker
  @private
  @param inst {object} The current instance settings.
  @param calendar {BaseCalendar} The current calendar.
  @param renderer {object} The rendering templates.
  @return {string} A week's worth of day headers.