QDateTime not accepted by QTableView

I am designing a major user interface with several fields and functions. However in order to shrink the problem I created a small application with 4 columns: name, image, dataDatabase, dateTime. I have a MainWindow with a QTableView, as soon as I right click inside the QTableView an AddItemDialog opens up with: 1) nameLineEdit, 2) ImLineEdit, 3) imageLineEdit 4) dateTimeEdit

The issue that I have is that I can't find a way to accept the 4) dateTimeEdit through the AddItemDialog. I didn't "go to slot" of the dateTimeEdit as I didn't think that I had to. I think that I am not doing the proper conversion for the date and time but please advise on what the issue might be.

I am including the most important parts of the application below with the related description of the procedure I followed:

I created an Item with the fields item.h:

class Item
{
public:
    Item(const double dateTime,
         const QString &name = "", const QString &image = "",
         const QByteArray &imagesData = QByteArray());
    QString name() const { return mName; }
    QString image() const { return mImage; }
    QByteArray imagesData() const { return mImagesData; }
    double dateTime() const { return mDateTime; }
private:
    QString mName;
    QString mImage;
    QByteArray mImagesData;
    double mDateTime;
};

and its related item.cpp

Item::Item(const double dateTime,
           const QString &name, const QString &image,
           const QByteArray &imagesData)
{
    mName = name;
    mImage = image;
    mImagesData = imagesData;
    mDateTime = dateTime;
}

I created a database.h table that will contain the parameters as follows:

class dataBase : public QObject
{
    Q_OBJECT
public:
    explicit dataBase(QObject *parent = nullptr);
    bool inizializationDataBase(const QString &nameDataBase);
    bool configureDataBase();
    QString getError() const { return mError; }
    bool addItem(const Item &item);
private:
    QSqlDatabase mDatabase;
    QString mError;
};

And its related database.cpp file - I am only including the most important piece of the code for this file:

#define CREATE_TABLE \
     " CREATE TABLE IF NOT EXISTS Fish_Table" \
     " (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL" \
     ", name TEXT NOT NULL" \
     ", image TEXT NOT NULL" \
     ", dataDataBase BLOB NOT NULL" \
     ", dateTime DOUBLE NOT NULL)"

dataBase::dataBase(QObject *parent)
    : QObject(parent)
{
}

bool dataBase::inizializationDataBase(const QString &nameDataBase) {
    // code
}

bool dataBase::addItem(const Item &item) {
    QSqlQuery q;
    q.prepare("INSERT INTO Fish_Table (name, image, dataDatabase, dateTime) VALUES (?,?,?,?)");
    q.addBindValue(item.name());
    q.addBindValue(item.image());
    q.addBindValue(item.imagesData());
    q.addBindValue(item.dateTime());
    bool ok = q.exec();
    if (!ok) {
        mError = q.lastError().text();
    }
    return ok;
}

and finally the AddItemDialog.h and AddItemDialog.cpp that contains the fields I am trying to pass to the QTableView of the MainWindow. AddItemDialog.h

namespace Ui
{
class AddItemDialog;
}

class AddItemDialog : public QDialog
{
    Q_OBJECT
public:
    explicit AddItemDialog(QWidget *parent = nullptr);
    ~AddItemDialog();
    Item item() const { return mItem; }
private slots:
    void on_toolButton_clicked();
    void on_buttonBox_accepted();
    void on_buttonBox_rejected();
private:
    Ui::AddItemDialog *ui;
    Item mItem;
};

AddItemDialog.cpp

AddItemDialog::AddItemDialog(QWidget *parent)
    : QDialog(parent)
    , ui(new Ui::AddItemDialog)
{
    ui->setupUi(this);
    auto fileSystemModel = new QFileSystemModel(this);
    fileSystemModel->setRootPath(QDir::rootPath());
    ui->imageLineEdit->setCompleter(new QCompleter(fileSystemModel,this));
    QDateTime dateTime;
    dateTime.setDate(QDate::currentDate());
}

AddItemDialog::~AddItemDialog()
{
    delete ui;
}

void AddItemDialog::on_toolButton_clicked()
{
    auto nameDataBase = QFileDialog::getOpenFileName(this, "Open Images", QDir::rootPath(),
                      "Images (*.png *.jpg *jpeg *.tif *.tiff);;Any type (*.*)");
    ui->imageLineEdit->setText(nameDataBase);
}

void AddItemDialog::on_buttonBox_accepted()
{
    QFile dataBase(ui->imageLineEdit->text());
    if (!dataBase.open(QIODevice::ReadOnly)) {
        QMessageBox::critical(this, "Error", dataBase.errorString());
        return;
    }
    mItem = Item(ui->nameLineEdit->text(),
                 ui->ImLineEdit->text(),dataBase.readAll());
    dataBase.close();
    accept();
}

So to recap: 1) I am not sure I provided the right format to the QDateTime conversion on the Item.h / Item.cpp and database.h / database.cpp 2) I am not sure how to pass the QDateTime from the AddItemDialog.cpp to the MainWindow

Additionally on the AddItemDialog.cpp I am having the following error right on the beginning: Constructor for AddItemDialog must explicitly initialize the member mItem which does not have a default constructor

Thanks for providing information on this issue that I have been having for a couple of days.