/**
 * date2比date1多的天数
 * @param date1 
 * @param date2
 * @return 
 */
 public static int differentDays(Date date1,Date date2)
 {
 Calendar cal1 = Calendar.getInstance();
 cal1.setTime(date1);
 
 Calendar cal2 = Calendar.getInstance();
 cal2.setTime(date2);
 int day1= cal1.get(Calendar.DAY_OF_YEAR);
 int day2 = cal2.get(Calendar.DAY_OF_YEAR);
 
 int year1 = cal1.get(Calendar.YEAR);
 int year2 = cal2.get(Calendar.YEAR);
 if(year1 != year2) //同一年
 {
  int timeDistance = 0 ;
  for(int i = year1 ; i < year2 ; i ++)
  {
  if(i%4==0 && i0!=0 || i%400==0) //闰年  
  {
   timeDistance += 366;
  }
  else //不是闰年
  {
   timeDistance += 365;
  }
  }
  
  return timeDistance + (day2-day1) ;
 }
 else //不同年
 {
  System.out.println("判断day2 - day1 : " + (day2-day1));
  return day2-day1;
 }
 }

　/**
 * 通过时间秒毫秒数判断两个时间的间隔
 * @param date1
 * @param date2
 * @return
 */
 public static int differentDaysByMillisecond(Date date1,Date date2)
 {
 int days = (int) ((date2.getTime() - date1.getTime()) / (1000*3600*24));
 return days;
 }

public static void main(String[] args) 
 {
 String dateStr = "2008-1-1 1:21:28";
 String dateStr2 = "2010-1-2 1:21:28";
 SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 try 
 {
  Date date2 = format.parse(dateStr2);
  Date date = format.parse(dateStr);
  
  System.out.println("两个日期的差距：" + differentDays(date,date2));
  System.out.println("两个日期的差距：" + differentDaysByMillisecond(date,date2));
 } catch (ParseException e) {
  e.printStackTrace();
 }
 }

public static void main(String[] args) 
 {
 String dateStr = "2015-1-1 21:21:28";
 String dateStr2 = "2015-1-2 1:21:28";
 SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 try 
 {
  Date date2 = format.parse(dateStr2);
  Date date = format.parse(dateStr);
  
  System.out.println("两个日期的差距：" + differentDays(date,date2));
  System.out.println("两个日期的差距：" + differentDaysByMillisecond(date,date2));
 } catch (ParseException e) {
  e.printStackTrace();
 }
 }