JS计算两个日期时间之差之天数不正确

 1 //定义目标日期
 2 var targetTime = new Date();
 3 
 4 //目标日期
 5 targetTime.setFullYear(2015,5,1);
 6 
 7 //目标时
 8 targetTime.setHours(12);
 9 
10 //目标分
11 targetTime.setMinutes(0);
12 
13 //目标秒
14 targetTime.setSeconds(0);
15 
16 //目标毫秒
17 targetTime.setMilliseconds(0);
18 
19 //转为毫秒数
20 var EndTime = targetTime.getTime();  
21 
22 //定义方法
23 function GetCountDownTime() {
24        
25             //定义参数返回当天的日期和时间
26             var NowTime = new Date();
27             
28             //得出时间毫秒差
29             var CountDownMS = EndTime - NowTime.getTime();
30             
31             //得出时间天数差
32             var CountDownDays = Math.floor(CountDownMS / (1000 * 60 * 60 * 24 ));
33 
34             //得出时间小时差
35             var CountDownH = Math.floor(CountDownMS / (1000 * 60 * 60)) % 24;
36 
37             //得出时间分钟差
38             var CountDownM = Math.floor(CountDownMS / (1000 * 60)) % 60;
39 
40             //得出时间秒数差
41             var CountDownS = Math.floor(CountDownMS / 1000) % 60;
42             }
43         } 
44 
45 
46 $(document).ready(function () {
47             window.setInterval("GetCountDownTime()", 1000);
48         });      

//目标日期
targetTime.setFullYear(2015,5,1);

//目标日期
targetTime.setFullYear(2015,4,1);