This is what help me fix my own

const CustomToolbar = ({date, onNavigate}: ToolbarProps)  => {

    const goToBack = () => {
        onNavigate('PREV');    }

    const goToNext = () => {
        onNavigate('NEXT');
        };

    return (
        <div className='rbc-toolbar'>
            <PrimaryButton onClick={goToBack} style={{marginRight: "5px"}} text='Previous'/>
            <DefaultButton onClick={goToNext} style={{marginRight: "5px"}} text='Next' />
            <DatePicker />
        </div>
    )
}