docs: public long addWrapField(long instant, int amount) {
          int thisValue = get(instant);
          int wrappedValue = FieldUtils.getWrappedValue
              (thisValue, amount, getMinimumValue(), getMaximumValue());
          // copy code from set() to avoid repeat call to get()
          return instant + (wrappedValue - thisValue) * getUnitMillis();
      }