java 日期 加减 运算

import java.util.Date;

import java.text.SimpleDateFormat;

import java.util.Calendar;

public class DateTest {

/**

* @param args

*/

public static void main(String[] args) throws Exception {

// TODO 自动生成方法存根

//日期相减算出秒的算法

Date date1 = new SimpleDateFormat("yyyy-mm-dd").parse("2005-06-08");

Date date2 = new SimpleDateFormat("yyyy-mm-dd").parse("2006-06-12");

long l = date1.getTime()-date2.getTime()>0 ? date1.getTime()-date2.getTime():

date2.getTime()-date1.getTime();

//System.out.println(l/1000+"秒");

//日期相减得到相差的日期

long day = (date1.getTime()-date2.getTime())/(24*60*60*1000)>0 ? (date1.getTime()-date2.getTime())/(24*60*60*1000):

(date2.getTime()-date1.getTime())/(24*60*60*1000);

long day1=date1.getTime();

Date sb = new Date();

sb.setTime(day1);

System.out.println(Ds(30));

// System.out.println("相差的日期: " +day);

}

public static String Ds(int days){

SimpleDateFormat form=new SimpleDateFormat("yyyy-MM-dd");

Calendar calendar = Calendar.getInstance();

int day = calendar.get(Calendar.DAY_OF_YEAR);

calendar.set(Calendar.DAY_OF_YEAR, day - days);

Date cc = calendar.getTime();

return form.format(cc);

}

}