js时间日期处理

//前几天的日期 
function getBeforeDate(n){
    var n = n;
    var d = new Date();
    var year = d.getFullYear();
    var mon=d.getMonth()+1;
    var day=d.getDate();
    if(day <= n){
            if(mon>1) {
               mon=mon-1;
            }
           else {
             year = year-1;
             mon = 12;
             }
           }
          d.setDate(d.getDate()-n);
          year = d.getFullYear();
          mon=d.getMonth()+1;
          day=d.getDate();
     s = year+"-"+(mon<10?('0'+mon):mon)+"-"+(day<10?('0'+day):day);
     return s;
}



//获取几天后的日期 

function GetDateStr(AddDayCount) { 
var dd = new Date(); 
dd.setDate(dd.getDate()+AddDayCount);
var y = dd.getFullYear(); 
var mm = dd.getMonth()+1;//获取当前月份的日期 
var d = dd.getDate(); 
var h = dd.getHours();
var m = dd.getMinutes();
var s = dd.getSeconds();
return y+"-"+mm+"-"+d +" "+h+":"+m+":"+s; 
} 





//两个日期时间差

function siteTime(){
window.setTimeout("siteTime()", 1000);
var seconds = 1000;
var minutes = seconds * 60;
var hours = minutes * 60;
var days = hours * 24;
var years = days * 365;
var today = new Date();
var todayYear = today.getFullYear();
var todayMonth = today.getMonth();
var todayDate = today.getDate();
var todayHour = today.getHours();
var todayMinute = today.getMinutes();
var todaySecond = today.getSeconds();
var t1 = Date.UTC(2013,11,24,21,16,09);
var t2 = Date.UTC(todayYear,todayMonth,todayDate,todayHour,todayMinute,todaySecond);
var diff = t2-t1;
var diffYears = Math.floor(diff/years);
var diffDays = Math.floor((diff/days)-diffYears*365);
var diffHours = Math.floor((diff-(diffYears*365+diffDays)*days)/hours);
var diffMinutes = Math.floor((diff-(diffYears*365+diffDays)*days-diffHours*hours)/minutes);
var diffSeconds = Math.floor((diff-(diffYears*365+diffDays)*days-diffHours*hours-diffMinutes*minutes)/seconds);
document.getElementById("run_day").innerHTML=(diffYears*365)+diffDays;
document.getElementById("run_hour").innerHTML=diffHours;
document.getElementById("run_minute").innerHTML=diffMinutes;
document.getElementById("run_second").innerHTML=diffSeconds;
}
siteTime();  //调用





//时间戳转日期
function   formatDate(d)   {    
     var   now=new   Date(d*1000); 
              var   year=now.getFullYear();     
              var   month=now.getMonth()+1;     
              var   date=now.getDate();     
              var   hour=now.getHours();     
              var   minute=now.getMinutes();     
              var   second=now.getSeconds();     
              return   year+"-"+month+"-"+date+" "+hour+":"+minute+":"+second;     
          }