增加日期时间

增加年：
Date addTime(int year) {
    Calendar cd = new GregorianCalendar();
    cd.setTime(new Date());
    cd.add(GregorianCalendar.YEAR, year);
    return cd.getTime();
}

增加月：
Date addTime(int month) {
    Calendar cd = new GregorianCalendar();
    cd.setTime(new Date());
    cd.add(GregorianCalendar.MONTH, month);
    return cd.getTime();
}

增加天数：
Date addTime(int day) {
    Calendar cd = new GregorianCalendar();
    cd.setTime(new Date());
    cd.add(GregorianCalendar.DAY_OF_MONTH, day);
    return cd.getTime();
}