code: public static DateFormat getInstance() {
          if (instance == null) {
              synchronized (instanceLock) {
                  if (instance == null) {
                      instance = new ResqueDateFormatThreadLocal();
                  }
              }
          }
          return instance.get();
      }
docs: NOTE: DateFormats returned from this method are for use by the caller's
  thread only.
  
  @return a configured DateFormat