日期加减(Calendar)

package test;

import java.text.SimpleDateFormat;
import java.util.Calendar; 
import java.util.Date;
 
public class DateCal {
 /**
  * @param args
  */
 public static void main(String[] args) throws Exception {

	 /**
	  * 当前日期
	  */
	  Calendar cal = Calendar.getInstance();    
	  cal.add(Calendar.DATE,-3);    
	  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");    
	  String now = sdf.format(cal.getTime());    
	  System.out.println("当前时间:"+now);    
	  
	  /**
	   * 日期相减
	   */
	  cal.set(2008, 01, 01);   
	  Date d1 = cal.getTime();   
	  cal.set(2008, 03, 01);   
	  Date d2 = cal.getTime();   
	  long daterange = d2.getTime() - d1.getTime();   
	  long time = 1000*3600*24; //A day in milliseconds
	  System.out.println("相差"+daterange/time+"天"); 
	  System.out.println("相差"+daterange/time/30+"个月");
	
	  /**
	   * 日期相加
	   */
	  sdf = new SimpleDateFormat("yyyy-MM-dd");
	  cal.setTime(sdf.parse("2008-01-01"));
	  cal.add(Calendar.DAY_OF_MONTH, +5); 
	  String result = sdf.format(cal.getTime()); 
	  System.out.println("相加/减后的日期:"+result);
 }
}

返回结果:
当前时间:2008-01-05 09:50:37
相差60天
相差2个月
相加/减后的日期:2008-01-06