code: public static final void setCurrentMillisOffset(long offsetMillis) throws SecurityException {
          checkPermission();
          if (offsetMillis == 0) {
              cMillisProvider = SYSTEM_MILLIS_PROVIDER;
          } else {
              cMillisProvider = new OffsetMillisProvider(offsetMillis);
          }
      }
docs: Sets the current time to return the system time plus an offset.
  <p>
  This method changes the behaviour of {@link #currentTimeMillis()}.
  Whenever the current time is queried, {@link System#currentTimeMillis()} is used
  and then offset by adding the millisecond value specified here.
  
  @param offsetMillis  the fixed millisecond time to use
  @throws SecurityException if the application does not have sufficient security rights