public void setTimeCorrectionMinutes(int minutes) {
    synchronized (mLock) {
      mPreferences.edit().putInt(PREFERENCE_KEY_OFFSET_MINUTES, minutes).commit();
      // Invalidate the cache to force reading actual settings from time to time
      mCachedCorrectionMinutes = null;
    }
  }
Sets the currently used time correction value.

@param minutes number of minutes by which this device is behind the correct time.
java/com/google/android/apps/authenticator/otp/TotpClock.java