<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
</head>

<body>
123
</body>
</html>
<script>
  var year = prompt("year","year");
  if(year!=null )
  {      
      if(year>=1 && year<=9999 && !isNaN(year) && year%1 ==0)
      {
          
          var month = prompt("month","month");
          if(month!=null )
          {      
              if(month>0 && month<13 && !isNaN(month) && month%1 ==0)
              {
                  var day = prompt("day","day");
                  if(day != null)
                  {
                      if(day<=31 && day>=1 && !isNaN(day) && day%1 ==0)
                      {
                          if(month==1||month==3||month==5||month==7||month==8||month==10||month==12)
                          {
                              alert(year+"年"+month+"月"+day+"日");
                          }
                          else if(month==4||month==6||month==9||month==11)
                          {
                              if(day<=30)
                              {
                                  alert(year+"年"+month+"月"+day+"日");
                              }
                              else
                              {
                                  alert("error1");
                              }
                          }
                          else  /*一定是2月*/
                          {
                              if(day<=28)
                              {
                                  alert(year+"年"+month+"月"+day+"日");
                              }
                              else 
                              {
                                  if(day==29)
                                  {
                                      if(year%4==0&&year%100!=0||year%400==0)
                                      {
                                          alert(year+"年"+month+"月"+day+"日");
                                      }
                                      else
                                      {
                                          alert("error2");
                                      }
                                  }
                                  else
                                  {
                                      alert("error3");
                                  }
                              }
                          }
                      }
                      else
                      {
                          alert("error4");
                      }
                  }
              }
              else
              {
                 alert("error5")
              }
          }      
          
      }
      else
      {
         alert("error6")
      }
  }
  
  
  
  
</script>