JAVA中的日期时间操作

    import java.util.Date;
    import java.text.SimpleDateFormat;
    import java.util.Calendar;
   //当前时间

   Calendar cal  = Calendar.getInstance();

   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

   String mDateTime=formatter.format(cal.getTime());

   out.println(mDateTime);

   out.println("<br>");

　//1年前日期

   java.util.Date myDate=new java.util.Date(); 

   long myTime=(myDate.getTime()/1000)-60*60*24*365;

   myDate.setTime(myTime*1000);

   String mDate=formatter.format(myDate);

   out.println(mDate);

   out.println("<br>");

　//明天日期

   myDate=new java.util.Date();

   myTime=(myDate.getTime()/1000)+60*60*24;

   myDate.setTime(myTime*1000);

   mDate=formatter.format(myDate);

   out.println(mDate);

   out.println("<br>");

　//两个时间之间的天数

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

   java.util.Date date= myFormatter.parse("2003-05-1");

   java.util.Date mydate= myFormatter.parse("1899-12-30");

   long  day=(date.getTime()-mydate.getTime())/(24*60*60*1000);

   out.println(day);

   out.println("<br>");

　//加半小时

   SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");

   java.util.Date date1 = format.parse("2002-02-28 23:16:00");

   long Time=(date1.getTime()/1000)+60*30;

   date1.setTime(Time*1000);

   String mydate1=formatter.format(date1);

   out.println(mydate1);

   out.println("<br>");

　//年月周求日期

   SimpleDateFormat formatter2 = new SimpleDateFormat("yyyy-MM F E");

   java.util.Date date2= formatter2.parse("2003-05 5 星期五");

   SimpleDateFormat formatter3 = new SimpleDateFormat("yyyy-MM-dd");

   String mydate2=formatter3.format(date2);

   out.println(mydate2);

   out.println("<br>");

　//求是星期几

   mydate= myFormatter.parse("2001-1-1");

   SimpleDateFormat formatter4 = new SimpleDateFormat("E");

   String mydate3=formatter4.format(mydate);

   out.println(mydate3);

   out.println("<br>");

//日期加减某些天、月、年

Calendar cal = Calendar.getInstance();//Get today´s date
cal.add(Calendar.DAY_OF_MONTH,20);
System.out.println("20 days later:"+cal.getTime());
cal.add(Calendar.DAY_OF_MONTH,-20);//Return back
cal.add(Calendar.MONTH,2);
System.out.println("2 month later:"+cal.getTime());
cal.add(Calendar.MONTH,-2);
cal.add(Calendar.YEAR,2);
System.out.println("2 years later:"+cal.getTime());