JAVA日期加减运算

	public static Date getBeforeMonth(Date date,int months)
	{
		Calendar calendar = Calendar.getInstance();      
		calendar.setTime(date);   
		calendar.set(Calendar.MONTH,calendar.get(Calendar.MONTH) - months);   
		return calendar.getTime();   
	}

 1.用java.util.Calender来实现,这种实现方式才是非常准确的

	public static String getBeforeDate(Date date,int days)
	{
		SimpleDateFormat df = new SimpleDateFormat(FORMAT_DAY);
		Calendar calendar = Calendar.getInstance();   
		calendar.setTime(date);
		calendar.set(Calendar.DAY_OF_YEAR,calendar.get(Calendar.DAY_OF_YEAR) - days);
		return df.format(calendar.getTime());
	}
	
	public static String getAfterDate(Date date,int days)
	{
		SimpleDateFormat df = new SimpleDateFormat(FORMAT_DAY);
		Calendar calendar = Calendar.getInstance();   
		calendar.setTime(date);
		calendar.set(Calendar.DAY_OF_YEAR,calendar.get(Calendar.DAY_OF_YEAR) + days);
		return df.format(calendar.getTime());
	}

 

 

2.用java.text.SimpleDateFormat和java.util.Date来实现

	public static String getBeforeDate(Date date,int days)
	{
		SimpleDateFormat df = new SimpleDateFormat(FORMAT_DAY);
		Date beforeDate = new Date(date.getTime() - days * 24 * 60 * 60 * 1000);
		return df.format(beforeDate);
	}
	
	public static String getAfterDate(Date date,int days)
	{
		SimpleDateFormat df = new SimpleDateFormat(FORMAT_DAY);
		Date beforeDate = new Date(date.getTime() + days * 24 * 60 * 60 * 1000);
		return df.format(beforeDate);
	}

 

3.获取月的第一天

	public static Date getMonthFirstDate(Date date)
	{
		Calendar calendar = Calendar.getInstance();      
		calendar.setTime(date);   
		calendar.set(Calendar.DAY_OF_MONTH,1);   
		calendar.set(Calendar.HOUR,0);   
		calendar.set(Calendar.MINUTE,0);  
		calendar.set(Calendar.SECOND,0);   
		return calendar.getTime();
	}

 

4.获取月的最后一天

	public static Date getMonthLastDate(Date date)
	{
		Calendar calendar = Calendar.getInstance();      
		calendar.setTime(date); 
		//先设置为下个月第一天
        calendar.add(Calendar.MONTH, 1);//加一个月
        calendar.set(Calendar.DATE, 1); //设置为该月第一天
		calendar.add(Calendar.DATE, -1);//再减一天即为上个月最后一天
		//设置时分秒
		calendar.set(Calendar.HOUR,23);   
		calendar.set(Calendar.MINUTE,59);  
		calendar.set(Calendar.SECOND,59);   
		return calendar.getTime();
	}
	

 

5. 月份加减

	public static Date getBeforeMonth(Date date,int months)
	{
		Calendar calendar = Calendar.getInstance();      
		calendar.setTime(date);   
		calendar.set(Calendar.MONTH,calendar.get(Calendar.MONTH) - months);   
		return calendar.getTime();   
	}