UTC的相互转换(java)

        SimpleDateFormat foo = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        System.out.println("foo:"+foo.format(new Date()));
        
        Calendar gc = GregorianCalendar.getInstance();
        System.out.println("gc.getTime():"+gc.getTime());
        System.out.println("gc.getTimeInMillis():"+new Date(gc.getTimeInMillis()));
        
        //当前系统默认时区的时间：
        Calendar calendar=new GregorianCalendar();
        System.out.print("时区："+calendar.getTimeZone().getID()+"  ");
        System.out.println("时间："+calendar.get(Calendar.HOUR_OF_DAY)+":"+calendar.get(Calendar.MINUTE));
        //美国洛杉矶时区
        TimeZone tz=TimeZone.getTimeZone("America/Los_Angeles");
        //时区转换
        calendar.setTimeZone(tz);
        System.out.print("时区："+calendar.getTimeZone().getID()+"  ");
        System.out.println("时间："+calendar.get(Calendar.HOUR_OF_DAY)+":"+calendar.get(Calendar.MINUTE));
        Date time=new Date();
        
        //1、取得本地时间：
        java.util.Calendar cal = java.util.Calendar.getInstance();

        //2、取得时间偏移量：
        int zoneOffset = cal.get(java.util.Calendar.ZONE_OFFSET);

        //3、取得夏令时差：
        int dstOffset = cal.get(java.util.Calendar.DST_OFFSET);

        //4、从本地时间里扣除这些差量，即可以取得UTC时间：
        cal.add(java.util.Calendar.MILLISECOND, -(zoneOffset + dstOffset));

        //之后调用cal.get(int x)或cal.getTimeInMillis()方法所取得的时间即是UTC标准时间。
        System.out.println("UTC:"+new Date(cal.getTimeInMillis()));
        
        Calendar calendar1 = Calendar.getInstance();
        TimeZone tztz = TimeZone.getTimeZone("GMT");       
        calendar1.setTimeZone(tztz);
        System.out.println(calendar.getTime());
        System.out.println(calendar.getTimeInMillis());