code: public PlainTime getStart(PlainTime context) {
  
          PlainTime compare = (
              (context.getHour() == 24)
              ? PlainTime.midnightAtStartOfDay()
              : context);
          PlainTime last = this.codeMap.lastKey();
  
          for (PlainTime key : this.codeMap.keySet()) {
              if (compare.isSimultaneous(key)) {
                  return key;
              } else if (compare.isBefore(key)) {
                  break;
              } else {
                  last = key;
              }
          }
  
          return last;
  
      }
docs: /*[deutsch]
  <p>Ermittelt den Start des Tagesabschnitts, der die angegebene Uhrzeit enth&auml;lt. </p>
  
  @param   context     the clock time a day period is searched for
  @return  start of day period around given clock time, inclusive
  @see     #getEnd(PlainTime)
  @since   3.13/4.10