Calendar类计算两个日期相差多少天

package bly;

import java.util.Calendar;

public class TestCalendar {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Calendar a = Calendar.getInstance(), b = Calendar.getInstance();
        a.set(2000, Calendar.SEPTEMBER, 13);
        b.set(2018, Calendar.JUNE, 28);
        long diffDays = (b.getTimeInMillis() - a.getTimeInMillis())
                / (1000 * 60 * 60 * 24);
        System.out.println("您已经活了：" + diffDays + " 天");
    }

}