UTC的相互轉換(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()));                //當前系統預設時區的時間：        Calendar calendar=new GregorianCalendar();        System.out.print("時區："+calendar.getTimeZone().getID()+"  ");        System.out.println("時間："+calendar.get(Calendar.HOUR_OF_DAY)+":"+calendar.get(Calendar.MINUTE));        //美國洛杉磯時區        TimeZone tz=TimeZone.getTimeZone("America/Los_Angeles");        //時區轉換        calendar.setTimeZone(tz);        System.out.print("時區："+calendar.getTimeZone().getID()+"  ");        System.out.println("時間："+calendar.get(Calendar.HOUR_OF_DAY)+":"+calendar.get(Calendar.MINUTE));        Date time=new Date();                //1、取得本地時間：        java.util.Calendar cal = java.util.Calendar.getInstance();        //2、取得時間位移量：        int zoneOffset = cal.get(java.util.Calendar.ZONE_OFFSET);        //3、取得夏令時差：        int dstOffset = cal.get(java.util.Calendar.DST_OFFSET);        //4、從本地時間裡扣除這些差量，即可以取得UTC時間：        cal.add(java.util.Calendar.MILLISECOND, -(zoneOffset + dstOffset));        //之後調用cal.get(int x)或cal.getTimeInMillis()方法所取得的時間即是UTC標準時間。        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());