Custom widget property being set after widget reload in action

class BirthdayMembersWidget extends BaseWidget
{
    public Carbon $startDate;

    public function mount(): void
    {
        $this->startDate = today();
    }

    protected function getTableHeaderActions(): array
    {
        return [
            Tables\Actions\Action::make('Next')
                ->label(new HtmlString('»'))
                ->action(function () {
                    $this->startDate = $this->startDate->addWeek();
                }),
        ];
    }

    protected function getTableQuery(): Builder
    {
        $startDate = $this->getStartDate();
        $endDate = $this->getEndDate();

        return User::query()
            ->select(['id', 'full_name', 'birthday'])
            ->whereBirthday($startDate, $endDate)
            ->orderByBirthday();
    }