How to use the @uifabric/date-time.DayOfWeek.Monday function in @uifabric/date-time

showWeekNumbers={true}
          firstWeekOfYear={1}
          showMonthPickerAsOverlay={true}
          placeholder="Select a date..."
          ariaLabel="Select a date"
        />

constructor(props: {}) {
    super(props);

    this.state = {
      firstDayOfWeek: DayOfWeek.Monday
    };
  }