直接上传代码：

import java.util.Calendar;
import java.text.SimpleDateFormat;
import java.text.ParseException;
public class CalendarDemo {
    public static void main(String[] args) throws ParseException {
        Calendar c = Calendar.getInstance();
        int year = c.get(Calendar.YEAR);
        int month = c.get(Calendar.MONTH);
        int day = c.get(Calendar.DAY_OF_MONTH);
        int hour = c.get(Calendar.HOUR_OF_DAY);
        int minute = c.get(Calendar.MINUTE);
        int second = c.get(Calendar.SECOND);
        System.out.println("今天是："+year+"年"+month+"月"+day+"日"+" "
                            +hour+":"+minute+":"+second);
        String hDay = "2017/09/10 12:00:00";
        String qDay = "2016/08/17 13:00:14";
        long days = calcDays(hDay, qDay);
        System.out.println(days);
    }
    public static long calcDays(String date1,String date2) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/ss HH:mm:ss");
        Calendar c = Calendar.getInstance();
        c.setTime(sdf.parse(date1));
        long time1 = c.getTimeInMillis();
        c.setTime(sdf.parse(date2));
        long time2 = c.getTimeInMillis();       
        return (time1-time2)/(24*3600*1000);
    }
}