计算过去时间

private static void extracted() {
    String date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(Calendar.getInstance().getTime());
    System.out.println("当前时间：" + date);

    SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Calendar c = Calendar.getInstance();

    c.setTime(new Date());
    c.add(Calendar.HOUR, -24);
    Date d1 = c.getTime();
    String hour = format.format(d1 );
    System.out.println("过去24小时：" + hour);

	c.setTime(new Date());
    c.add(Calendar.DATE, -3);
    Date d2  = c.getTime();
    String day1 = format.format(d2 );
    System.out.println("过去3天：" + day1);

    c.setTime(new Date());
    c.add(Calendar.DATE, -7);
    Date d2  = c.getTime();
    String day2 = format.format(d2 );
    System.out.println("过去7天：" + day2);

    c.setTime(new Date());
    c.add(Calendar.MONTH, -1);
    Date d3  = c.getTime();
    String mon = format.format(d3);
    System.out.println("过去1个月：" + mon);

    c.setTime(new Date());
    c.add(Calendar.MONTH, -3);
    Date d4 = c.getTime();
    String mon2 = format.format(d4);
    System.out.println("过去3个月：" + mon2);

    c.setTime(new Date());
    c.add(Calendar.YEAR, -1);
    Date d5 = c.getTime();
    String year = format.format(d5);
    System.out.println("过去1年：" + year);
}