Date.prototype.dateDiff = function(interval,objDate){
    if(arguments.length<2||objDate.constructor!=Date) return undefined;
    switch (interval) {
      case "d":return parseInt((objDate-this)/86400000);
      default:return undefined;
    }
  }
var sDT = new Date();
var gqst="离过期还有";
if (sDT.dateDiff("d",eDT)==0){
gqst="今天过期";
}
if (sDT.dateDiff("d",eDT)<0){
gqst="<font color=\"#FF0000\">已经过期！</font>";
}
if (sDT.dateDiff("d",eDT)>0){
gqst=gqst+sDT.dateDiff("d",eDT)+"天";
}
if (zutz==0){
document.writeln(gqst);
}