c# - Custom NextMonth CallenderControll button bug -

so need make custom next/prev button , got work jsut has litle problem displaying right number in label reason shows day before 1 callender showing if december display 11th in label think postback cant figure out after hours of frustration im gonna try , ask here have far

source code backend

private int month; private int year; private datetime date;  void dayrender(object source, dayrendereventargs e) {     // change background color of days in month     // yellow.     if (!e.day.isothermonth && !e.day.isweekend)         e.cell.backcolor = system.drawing.color.yellow;      // add custom text cell in calendar control.     if (e.day.date.day == 18)         e.cell.controls.add(new literalcontrol("<br />holiday")); }  protected void page_load(object sender, eventargs e) {     if (!ispostback)     {         date = datetime.now;         calendrier.visibledate = date;         month = date.month;         session["month"] = month;         year = date.year;     }     monthlabel.text = session["month"].tostring(); } // when next button being clicked protected void nextmonth_command(object sender, commandeventargs e) {     int sessionmonth;      sessionmonth = convert.toint32(session["month"]);     sessionmonth++;     session["month"] = sessionmonth;     changecallender(2000, sessionmonth); }  // method add date callender private void changecallender(int year, int month) {     datetime date = new datetime(year , month, 1);     calendrier.visibledate = date; }