public long roundCeiling(long instant) {
   if (iTimeField) {
     int offset = getOffsetToAdd(instant);
     instant = iField.roundCeiling(instant + offset);
     return instant - offset;
   } else {
     long localInstant = iZone.convertUTCToLocal(instant);
     localInstant = iField.roundCeiling(localInstant);
     return iZone.convertLocalToUTC(localInstant, false, instant);
   }
 }