java - Java 中的日历...我对两个不同的值得到相同的结果

Question

    Calendar cal = Calendar.getInstance();
    long now = cal.getTimeInMillis();
    int year = 2014;
    int month = 3;
    int date = 8;
    cal.set(year, month - 1, date);
    long dday = cal.getTimeInMillis();
    long count = (dday - now) / (1000 * 24 * 60 * 60);
    System.out.println((dday - now));
    System.out.println(count);

此代码计算从现在到某个日期之间的天数。但是，我在 3 月 8 日和 3 月 9 日得到了相同的结果。请帮忙!提前谢谢你。

---

更详细的源代码示例，作者 Basil Bourque。

Calendar cal = Calendar.getInstance();
long nowInMillis = cal.getTimeInMillis();

cal.set( 2014, Calendar.MARCH, 8 );  // March 8, 2014   // year, month, day
long march_8_2014_inMillis = cal.getTimeInMillis();

cal.set( 2014,  Calendar.MARCH, 9 );  // March 9, 2014   // year, month, day
long march_9_2014_inMillis = cal.getTimeInMillis();

long daysTil8th = ( march_8_2014_inMillis - nowInMillis ) / ( 1000 * 24 * 60 * 60 );
long daysTil9th = ( march_9_2014_inMillis - nowInMillis ) / ( 1000 * 24 * 60 * 60 );

System.out.println( "( march_8_2014_inMillis - nowInMillis ) in artificial days: " + daysTil8th + ", in milliseconds: " + ( march_8_2014_inMillis - nowInMillis ) );
System.out.println( "( march_9_2014_inMillis - nowInMillis ) in artificial days: " + daysTil9th + ", in milliseconds: " + ( march_9_2014_inMillis - nowInMillis ) );

System.out.println( "( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ): " + ( ( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ) ) ) ;
System.out.println( "( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ) / ( 1000 * 60 * 60 ): " + ( ( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ) ) / ( 1000 * 60 * 60 ) ) ;

在 2013-11-20T17:35:01.119-08:00(太平洋标准时间)在西雅图、Java 7、Mac OS X 10.8.5 运行时......

( march_8_2014_inMillis - nowInMillis ) in artificial days: 108, in milliseconds: 9331200000
( march_9_2014_inMillis - nowInMillis ) in artificial days: 108, in milliseconds: 9414000000
( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ): 82800000
( march_9_2014_inMillis - nowInMillis ) - ( march_8_2014_inMillis - nowInMillis ) / ( 1000 * 60 * 60 ): 23

注意:对于我所在的时区，DST 2014 年 3 月 9 日星期日凌晨 2:00 开始。

问题:为什么在上面的两行输出中都是 108？答案是 DST，但究竟如何？

Answer 1

3 月 9 日是 2014 年夏令时转换的日子。因此，计算正确，3 月 9 日相差 108 天 23 小时，四舍五入为 108 天。