JavaScript中 日期的计算(转)

出处：http://www.cnblogs.com/joey0210/archive/2013/01/15/JavaScript%E6%97%B6%E9%97%B4%E8%AE%A1%E7%AE%97.html

项目中经常要 计算当前时间 加多少天后的时间，找到三不错的方法，记录下来。摘自：http://www.blogjava.net/jimingminlovefly/articles/363157.html。

1.计算当前日期+N天后的日期
function CurrentDateAddDay(n){
 var s, d, t, t2;
 t = new Date().getTime();
    t2 = n * 1000 * 3600 * 24;
    t+= t2;
    d = new Date(t);
    s = d.getUTCFullYear() + "-";
    s += ("00"+(d.getUTCMonth()+1)).slice(-2) + "-";
    s += ("00"+d.getUTCDate()).slice(-2);
    return s;
} 

2.计算给定日期后的N天
function DateAddDay(str,n){   
  var   dd, mm, yy;   
  var   reg = /^(\d{4})-(\d{1,2})-(\d{1,2})$/;
  if (arr = str.match(reg)) {
    yy = Number(arr[1]);
    mm = Number(arr[2])-1;
    dd = Number(arr[3]);
  } else {
    var d = new Date();
    yy = d.getUTCFullYear();
    mm = ("00"+(d.getUTCMonth())).slice(-2);
    dd = ("00"+d.getUTCDate()).slice(-2);
  }
  return date2str(yy, mm, dd,n);
} 

3.计算给定日期后的N天
function SpecifiedDateAddDay(yy, mm, dd,n) {
    var s, d, t, t2;
    t = Date.UTC(yy, mm, dd);
    t2 = n * 1000 * 3600 * 24;
    t+= t2;
    d = new Date(t);
    s = d.getUTCFullYear() + "-";
    s += ("00"+(d.getUTCMonth()+1)).slice(-2) + "-";
    s += ("00"+d.getUTCDate()).slice(-2);
    return s;
}