How to use the @commercetools-uikit/calendar-time-utils.getStartOf function in @commercetools-uikit/calendar-time-utils

handleTimeChange = event => {
    const parsedTime = parseTime(event.target.value);

    this.setState({ timeString: event.target.value });

    // We can't update the parent when there is no value
    if (this.props.value === '') return;

    let date = getStartOf(this.props.value, this.props.timeZone);
    if (parsedTime) {
      date = changeTime(date, this.props.timeZone, parsedTime);
    }
    this.emit(date);
  };
  emit = value =>