code: public ZonedDateTime getStartZonedDateTime() {
          if (zonedStartDateTime == null) {
              zonedStartDateTime = ZonedDateTime.of(startDate, startTime, zoneId);
          }
  
          return zonedStartDateTime;
      }
docs: A convenience method to retrieve a zoned date time based on the start
  date, start time, and time zone id.
  
  @return the zoned start time