_triggerToggleDate(date) {
    if (!this.props.disabled && !this.props.readOnly) {
      let day;
      let month;
      let year;
      if (this.state.selectedDate && date &&
          this.state.selectedDate.getDate() === date.getDate() && this.state.selectedDate.getMonth() === date.getMonth() && this.state.selectedDate.getFullYear() === date.getFullYear()) {
        day = undefined;
        month = this.state.month;
        year = this.state.year;
      } else {
        day = date.getDate();
        month = date.getMonth();
        year = date.getFullYear();
      }

      this._triggerSelectDate(day, month, year);
    }
  }
Function will select / deselect date passed to it, it is used in case of 'Space' keyDown on a day.