docs: public long getMillisKeepLocal(DateTimeZone newZone, long oldInstant) {
          if (newZone == null) {
              newZone = DateTimeZone.getDefault();
          }
          if (newZone == this) {
              return oldInstant;
          }
          long instantLocal = convertUTCToLocal(oldInstant);
          return newZone.convertLocalToUTC(instantLocal, false, oldInstant);
      }