code: public long addWrapField(long instant, int months) {
          return set(instant, FieldUtils.getWrappedValue(get(instant), months, MIN, iMax));
      }
docs: Add to the Month component of the specified time instant
  wrapping around within that component if necessary.
  
  @see org.joda.time.DateTimeField#addWrapField
  @param instant  the time instant in millis to update.
  @param months  the months to add (can be negative).
  @return the updated time instant.