code: void formatMonth(StringBuilder b, ZonedDateTime d, int width, FieldVariants months) {
      int month = d.getMonth().getValue();
      switch (width) {
        case 5:
          b.append(months.narrow[month-1]);
          break;
  
        case 4:
          b.append(months.wide[month-1]);
          break;
  
        case 3:
          b.append(months.abbreviated[month-1]);
          break;
  
        case 2:
          if (month < 10) {
            b.append('0');
          }
          // fall through
  
        case 1:
          b.append(month);
          break;
      }
    }
docs: Format the month, numeric or a string name variant.