Отпуск:
SimpleDateFormat sf = new SimpleDateFormat("E, dd MMM yyyy HH:mm:ss z", Locale.ENGLISH);
sf.setCalendar(Calendar.getInstance(TimeZone.getTimeZone("GMT")));
Calendar calendar = Calendar.getInstance();
Date now = calendar.getTime();
calendar.add(Calendar.HOUR,-1);
Date earlierTime = calendar.getTime();
System.out.println(sf.format(now)); // output: Thu, 06 Oct 2011 11:53:58 GMT
System.out.println(sf.format(earlierTime)); // output: Thu, 06 Oct 2011 10:53:58 GMT