code: public LocalDateTime getStartDateTime() {
          if (startDateTime == null) {
              startDateTime = LocalDateTime.of(getStartDate(), getStartTime());
          }
  
          return startDateTime;
      }
docs: Utility method to get the local start date time. This method combines the
  start date and the start time to create a date time object.
  
  @return the start local date time
  @see #getStartDate()
  @see #getStartTime()