Set form field value from outside the form

class EditModel
{
    #[On('set-date')]
    public function updateDateFormField($date)
    {
        $this->data['date'] = $date;
    }

    public function form(Form $form): Form
    {
        return $form
            ->schema([
                DatePicker::make('date'),
                ...
            ])
            ->statePath('data');
    }
}