//之前N天日期...
			function getBeforeDate(n){
				var date=new Date();
				var t=date.getTime(); 
				var x=t-(24*60*60*1000)*n;
				var d=new Date(); 
					d.setTime(x); 
				var monthname=new Array("01","02","03","04","05","06","07","08","09","10","11","12");
				var ri=''+d.getDate()+'';
				var resultDate='';
				if(ri.length==1){
					var resultDate = d.getFullYear()+"-"+ monthname[d.getMonth()]+"-0"+d.getDate();
				}else{
					var resultDate = d.getFullYear()+"-"+ monthname[d.getMonth()]+"-"+d.getDate();
				}
				return resultDate;
			}
			
			//某个日期的前N天
			function getBeforDateByOneDate(_date,n){
				var date = strToDate(_date);
				var t=date.getTime(); 
				var x=t-(24*60*60*1000)*n;
				var d=new Date(); 
					d.setTime(x); 
				var monthname=new Array("01","02","03","04","05","06","07","08","09","10","11","12");
				var ri=''+d.getDate()+'';
				var resultDate='';
				if(ri.length==1){
					var resultDate = d.getFullYear()+"-"+ monthname[d.getMonth()]+"-0"+d.getDate();
				}else{
					var resultDate = d.getFullYear()+"-"+ monthname[d.getMonth()]+"-"+d.getDate();
				}
				return resultDate;
			}
			//时间减时间
			function dateSubtration(_date1,_date2){
				var _date11 = strToDate(_date1);
				var _date22 = strToDate(_date2);
				var df=(_date11.getTime()-_date22.getTime())/3600/1000/24; 
				return df;
			}
			//字符串转换成日期对象
			function strToDate(str)
			{
			  var arys= new Array();
			  arys=str.split('-');
			  var newDate=new Date(arys[0],arys[1]-1,arys[2]); 
			  return newDate;
			} 
			
			// 实时显示当前时间
			function showtime() {
				var today,hour,second,minute,year,month,date;
				var strDate ;
				   today=new Date();
				 var n_day = today.getDay();
				 switch (n_day)
				 {
				 case 0:{
				 strDate = "星期日"
				 }break;
				 case 1:{
				 strDate = "星期一"
				 }break;
				 case 2:{
				 strDate ="星期二"
				 }break;
				 case 3:{
				 strDate =  "星期三"
				 }break;
				 case 4:{
				 strDate =  "星期四"
				 }break;
				 case 5:{
				 strDate =  "星期五"
				 }break;
				 case 6:{
				 strDate =  "星期六"
				 }break;
				 case 7:{
				 strDate =  "星期日"
				 }break;
				 }
				year = today.getYear();
				month = today.getMonth()+1;
				date = today.getDate();
				hour = today.getHours();
				minute =today.getMinutes();
				second = today.getSeconds();
				document.getElementById('time').innerHTML = "今天是"+year + "年" + month + "月" + date + "日 " +  strDate +" " + hour + ":" + minute + ":" + second; //显示时间
				setTimeout("showtime();", 1000); //设定函数自动执行时间为 1000 ms(1 s)
}