Java中两个日期之间的天差异？

我需要找到两个日期之间的天数 ：一个来自报告，另一个来自当前日期。 我的片段：

  int age=calculateDifference(agingDate, today);

这里calculateDifference是一个私有方法， agingDate和today是Date对象，仅供您澄清。 我已经从Java论坛中发表了两篇文章，即Thread 1 / Thread 2。

它可以在独立程序中正常工作，但是当我将这些内容包含在我的逻辑中以便从报告中读取时，我会发现数值上的差异。

为什么会发生这种情况，我该如何解决它？

编辑：

与实际天数相比，我得到的天数更多。

public static int calculateDifference(Date a, Date b)
{
    int tempDifference = 0;
    int difference = 0;
    Calendar earlier = Calendar.getInstance();
    Calendar later = Calendar.getInstance();

    if (a.compareTo(b) < 0)
    {
        earlier.setTime(a);
        later.setTime(b);
    }
    else
    {
        earlier.setTime(b);
        later.setTime(a);
    }

    while (earlier.get(Calendar.YEAR) != later.get(Calendar.YEAR))
    {
        tempDifference = 365 * (later.get(Calendar.YEAR) - earlier.get(Calendar.YEAR));
        difference += tempDifference;

        earlier.add(Calendar.DAY_OF_YEAR, tempDifference);
    }

    if (earlier.get(Calendar.DAY_OF_YEAR) != later.get(Calendar.DAY_OF_YEAR))
    {
        tempDifference = later.get(Calendar.DAY_OF_YEAR) - earlier.get(Calendar.DAY_OF_YEAR);
        difference += tempDifference;

        earlier.add(Calendar.DAY_OF_YEAR, tempDifference);
    }

    return difference;
}

注意 ：

不幸的是，没有任何答案帮助我解决了这个问题。 我在Joda时间库的帮助下完成了这个问题。

---

我建议你使用卓越的Joda时间库，而不是有缺陷的java.util.Date和朋友。 你可以简单地写

import java.util.Date;
import org.joda.time.DateTime;
import org.joda.time.Days;

Date past = new Date(110, 5, 20); // June 20th, 2010
Date today = new Date(110, 6, 24); // July 24th 
int days = Days.daysBetween(new DateTime(past), new DateTime(today)).getDays(); // => 34

---

我可能为时太晚而无法参加比赛，但这到底是怎么回事？ :)

你认为这是一个线程问题？ 你如何使用这种方法的输出？ 要么

我们可以改变你的代码来做一些简单的事情：

Calendar calendar1 = Calendar.getInstance();
    Calendar calendar2 = Calendar.getInstance();
    calendar1.set(<your earlier date>);
    calendar2.set(<your current date>);
    long milliseconds1 = calendar1.getTimeInMillis();
    long milliseconds2 = calendar2.getTimeInMillis();
    long diff = milliseconds2 - milliseconds1;
    long diffSeconds = diff / 1000;
    long diffMinutes = diff / (60 * 1000);
    long diffHours = diff / (60 * 60 * 1000);
    long diffDays = diff / (24 * 60 * 60 * 1000);
    System.out.println("nThe Date Different Example");
    System.out.println("Time in milliseconds: " + diff
 + " milliseconds.");
    System.out.println("Time in seconds: " + diffSeconds
 + " seconds.");
    System.out.println("Time in minutes: " + diffMinutes 
+ " minutes.");
    System.out.println("Time in hours: " + diffHours 
+ " hours.");
    System.out.println("Time in days: " + diffDays 
+ " days.");
  }

---

diff /（24 *等）不考虑Timezone，所以如果你的默认时区有一个DST，它可以关闭计算。

这个链接有一个不错的实现。

如果链接出现故障，这里是上述链接的来源：

/** Using Calendar - THE CORRECT WAY**/  
public static long daysBetween(Calendar startDate, Calendar endDate) {  
  //assert: startDate must be before endDate  
  Calendar date = (Calendar) startDate.clone();  
  long daysBetween = 0;  
  while (date.before(endDate)) {  
    date.add(Calendar.DAY_OF_MONTH, 1);  
    daysBetween++;  
  }  
  return daysBetween;  
}  

和

/** Using Calendar - THE CORRECT (& Faster) WAY**/  
public static long daysBetween(final Calendar startDate, final Calendar endDate)
{
  //assert: startDate must be before endDate  
  int MILLIS_IN_DAY = 1000 * 60 * 60 * 24;  
  long endInstant = endDate.getTimeInMillis();  
  int presumedDays = 
    (int) ((endInstant - startDate.getTimeInMillis()) / MILLIS_IN_DAY);  
  Calendar cursor = (Calendar) startDate.clone();  
  cursor.add(Calendar.DAY_OF_YEAR, presumedDays);  
  long instant = cursor.getTimeInMillis();  
  if (instant == endInstant)  
    return presumedDays;

  final int step = instant < endInstant ? 1 : -1;  
  do {  
    cursor.add(Calendar.DAY_OF_MONTH, step);  
    presumedDays += step;  
  } while (cursor.getTimeInMillis() != endInstant);  
  return presumedDays;  
}

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