code: static HijriAdjustment from(String variant) {
  
          int index = variant.indexOf(':');
  
          if (index == -1) {
              return new HijriAdjustment(variant, 0);
          } else {
              try {
                  int adjustment = Integer.parseInt(variant.substring(index + 1));
                  return new HijriAdjustment(variant.substring(0, index), adjustment);
              } catch (NumberFormatException nfe) {
                  throw new ChronoException("Invalid day adjustment: " + variant);
              }
          }
  
      }
docs: also called by Hijri calendar systems