JS获取系统的指定定年月日

 /**
  * 获取系统当前时间
  */
 function getNowYearMouth(){
      var date=new Date;
      var nowYearMouth=date.getMonth()+1;
      var year=date.getFullYear();
       var day = date.getDate();
      nowYearMouth =(nowYearMouth<10 ? "0"+nowYearMouth:nowYearMouth);    //获取当前时间----月份
      var nowYearMouthCur = (year.toString()+"-"+nowYearMouth.toString());  //获取当前时间----年月
      var beforsixYearMouthday= getBeforeYearMouthDay();
      return  nowYearMouthCur;
 }

 /**
  * 获取系统当前年月日
  */
 function getNowYearMouthDay(){
      var date=new Date;
      var nowYearMouth=date.getMonth()+1;
      var year=date.getFullYear();
       var day = date.getDate();
      nowYearMouth =(nowYearMouth<10 ? "0"+nowYearMouth:nowYearMouth);    //获取当前时间----月份
      day=(day<10?"0"+day:day);
      var nowYearMouthDay = (year.toString()+"-"+nowYearMouth.toString()+"-"+day.toString());//获取系统当前的年月日
      return nowYearMouthDay;
 }

 /**
  * 获取系统前六个月时间--年月
  */
 function getbeforeYearMouth()  {
      var date=new Date;
 //     date = new Date( date - 86400000 * 30 * 10 );
      var month=date.getMonth()+1;
      var year=date.getFullYear();
      for (var i=0;i<6;i++)
      {
          if(month<=0)
          {
              month = month+12;
              year--;
          }
          var tempmonth =(month<10 ? "0"+month:month);
          var mydate = year.toString()+"-"+tempmonth.toString();
          month--;
      }
      return mydate;
 }
 /**
  * 获取系统前六个月的年月日
  */
 function getBeforeYearMouthDay(){
     var tempmonth;
     var date=new Date;
     var month=date.getMonth()+1;
     var year=date.getFullYear();
     var day = date.getDate();
     for (var i=0;i<=12;i++){
         if(month<=0) {
             month = month+12;
             year--;
         }
         tempmonth =(month<10 ? "0"+month:month);
       month--;
     }
     if((year%100!=0)&(year%400==0)&&(year%4==0)){//是闰年的情况下
             if(tempmonth==2){  //若果是2月份
                 if(day>29){
                     tempmonth = tempmonth+1;
                 }else{
                     tempmonth = tempmonth;
                 }
                 }else{//不是2月份的情况
                     tempmonth = tempmonth;
                 }
             }else{//不是闰年的情况下
                 if(tempmonth==2){  //若果是2月份
                     if(day>28){
                         tempmonth = tempmonth+1;
                     }else{
                         tempmonth = tempmonth;
                     }
                 }else{//不是2月份的情况
                         tempmonth = tempmonth;
                     }
             }
     if(day<10){
         day="0"+day;
     }
    var beforeYearMouthDay = year.toString()+"-"+tempmonth.toString()+"-"+day.toString();
    return beforeYearMouthDay;
 }