docs: public static LocalDateTime fromCalendarFields(Calendar calendar) {
          if (calendar == null) {
              throw new IllegalArgumentException("The calendar must not be null");
          }
          int era = calendar.get(Calendar.ERA);
          int yearOfEra = calendar.get(Calendar.YEAR);
          return new LocalDateTime(
              (era == GregorianCalendar.AD ? yearOfEra : 1 - yearOfEra),
              calendar.get(Calendar.MONTH) + 1,
              calendar.get(Calendar.DAY_OF_MONTH),
              calendar.get(Calendar.HOUR_OF_DAY),
              calendar.get(Calendar.MINUTE),
              calendar.get(Calendar.SECOND),
              calendar.get(Calendar.MILLISECOND)
          );
      }