CalendarDateSelect.prototype.initHeaderDiv = function() {
    var header_div = this.header_div;
    this.close_button = header_div.build("a", { innerHTML: "x", href:"#", onclick:function () { this.close(); return false; }.bindAsEventListener(this), className: "close" });
    this.next_month_button = header_div.build("a", { innerHTML: ">", href:"#", onclick:function () { this.navMonth(this.date.getMonth() + 1 ); return false; }.bindAsEventListener(this), className: "next" });
    this.prev_month_button = header_div.build("a", { innerHTML: "<", href:"#", onclick:function () { this.navMonth(this.date.getMonth() - 1 ); return false; }.bindAsEventListener(this), className: "prev" });
    
    if (this.options.get("month_year")=="dropdowns") {
      this.year_select = new SelectBox(header_div, [], {className: "year", onchange: function () { this.navYear(this.year_select.getValue()) }.bindAsEventListener(this)}); 
      header_div.build("span", {innerHTML: "年 ", className: "nentsuki" });
      this.month_select = new SelectBox(header_div, $R(0,11).map(function(m){return [Date.months[m], m]}), {className: "month", onchange: function () { this.navMonth(this.month_select.getValue()) }.bindAsEventListener(this)}); 
      header_div.build("span", {innerHTML: "月", className: "nentsuki" });
      this.populateYearRange();
    } else {
      this.month_year_label = header_div.build("span")
    }
  };