以下是一种解决方案，因为我们有许多方法可以实现这一点:

  import java.util.*; 
   int syear = 2000;
   int eyear = 2000;
   int smonth = 2;//Feb
   int emonth = 3;//Mar
   int sday = 27;
   int eday = 1;
   Date startDate = new Date(syear-1900,smonth-1,sday);
   Date endDate = new Date(eyear-1900,emonth-1,eday);
   int difInDays = (int) ((endDate.getTime() - startDate.getTime())/(1000*60*60*24));

试试这个:

int epoch = (int) (new java.text.SimpleDateFormat("MM/dd/yyyy HH:mm:ss").parse("01/01/1970  00:00:00").getTime() / 1000);

你可以在parse()方法参数中编辑字符串。

如果你想修复跨越夏时制边界的日期范围的问题(例如，一个日期在夏季，另一个日期在冬季)，你可以使用这个来获得天数的差异:

public static long calculateDifferenceInDays(Date start, Date end, Locale locale) {
    Calendar cal = Calendar.getInstance(locale);

    cal.setTime(start);
    cal.set(Calendar.HOUR_OF_DAY, 0);
    cal.set(Calendar.MINUTE, 0);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MILLISECOND, 0);
    long startTime = cal.getTimeInMillis();

    cal.setTime(end);
    cal.set(Calendar.HOUR_OF_DAY, 0);
    cal.set(Calendar.MINUTE, 0);
    cal.set(Calendar.SECOND, 0);
    cal.set(Calendar.MILLISECOND, 0);
    long endTime = cal.getTimeInMillis();

    // calculate the offset if one of the dates is in summer time and the other one in winter time
    TimeZone timezone = cal.getTimeZone();
    int offsetStart = timezone.getOffset(startTime);
    int offsetEnd = timezone.getOffset(endTime);
    int offset = offsetEnd - offsetStart;

    return TimeUnit.MILLISECONDS.toDays(endTime - startTime + offset);
}

int daysDiff = (date1.getTime() - date2.getTime()) / MILLIS_PER_DAY;

我喜欢基于timeunit的方法，直到我发现它只覆盖了一个时间单元在下一个更高单位中有多少个单位是固定的这种微不足道的情况。当你想知道间隔了多少个月、多少年等时，这个问题就不成立了。

这里有一种计数方法，不像其他方法那么有效，但它似乎对我有用，而且还考虑到了夏令时。

public static String getOffsetAsString( Calendar cNow, Calendar cThen) {
    Calendar cBefore;
    Calendar cAfter;
    if ( cNow.getTimeInMillis() < cThen.getTimeInMillis()) {
        cBefore = ( Calendar) cNow.clone();
        cAfter = cThen;
    } else {
        cBefore = ( Calendar) cThen.clone();
        cAfter = cNow;
    }
    // compute diff
    Map<Integer, Long> diffMap = new HashMap<Integer, Long>();
    int[] calFields = { Calendar.YEAR, Calendar.MONTH, Calendar.DAY_OF_MONTH, Calendar.HOUR_OF_DAY, Calendar.MINUTE, Calendar.SECOND, Calendar.MILLISECOND};
    for ( int i = 0; i < calFields.length; i++) {
        int field = calFields[ i];
        long    d = computeDist( cAfter, cBefore, field);
        diffMap.put( field, d);
    }
    final String result = String.format( "%dY %02dM %dT %02d:%02d:%02d.%03d",
            diffMap.get( Calendar.YEAR), diffMap.get( Calendar.MONTH), diffMap.get( Calendar.DAY_OF_MONTH), diffMap.get( Calendar.HOUR_OF_DAY), diffMap.get( Calendar.MINUTE), diffMap.get( Calendar.SECOND), diffMap.get( Calendar.MILLISECOND));
    return result;
}

private static int computeDist( Calendar cAfter, Calendar cBefore, int field) {
    cBefore.setLenient( true);
    System.out.print( "D " + new Date( cBefore.getTimeInMillis()) + " --- " + new Date( cAfter.getTimeInMillis()) + ": ");
    int count = 0;
    if ( cAfter.getTimeInMillis() > cBefore.getTimeInMillis()) {
        int fVal = cBefore.get( field);
        while ( cAfter.getTimeInMillis() >= cBefore.getTimeInMillis()) {
            count++;
            fVal = cBefore.get( field);
            cBefore.set( field, fVal + 1);
            System.out.print( count + "/"  + ( fVal + 1) + ": " + new Date( cBefore.getTimeInMillis()) + " ] ");
        }
        int result = count - 1;
        cBefore.set( field, fVal);
        System.out.println( "" + result + " at: " + field + " cb = " + new Date( cBefore.getTimeInMillis()));
        return result;
    }
    return 0;
}

这是另一个样本。基本上适用于用户定义的模式。

   public static LinkedHashMap<String, Object> checkDateDiff(DateTimeFormatter dtfObj, String startDate, String endDate)
   {
          Map<String, Object> dateDiffMap = new HashMap<String, Object>();
          DateTime start = DateTime.parse(startDate,dtfObj);
          DateTime end = DateTime.parse(endDate,dtfObj);
          Interval interval = new Interval(start, end);
          Period period = interval.toPeriod();

          dateDiffMap.put("ISO-8601_PERIOD_FORMAT", period);
          dateDiffMap.put("YEAR", period.getYears());
          dateDiffMap.put("MONTH", period.getMonths());
          dateDiffMap.put("WEEK", period.getWeeks());
          dateDiffMap.put("DAY", period.getWeeks());             
          dateDiffMap.put("HOUR", period.getHours());
          dateDiffMap.put("MINUTE", period.getMinutes());
          dateDiffMap.put("SECOND", period.getSeconds());

          return dateDiffMap;        
   }