When QDate in C++ is passes to Date in QML, converts to the previous day string in Qt 5.15.

m.kawakami

When QDate in C++ passes to Date in QML, My program in Qt 5.15 converts to the previous day string.

I guess what occurs in Qt6.2 Document says.

Qt 6.2 Document

If your program is run in a zone behind UTC (nominally west of The Prime Meridian), use of a date-only string will lead to a object whose is one less than the day-number in your string; i

But, Qt 5.15 document doesn't say it.

Qt 5.15 Document

I have questions below.

Is this also occur at Qt 5.15?
I don't want to change QDate to QDatetime as possible. Can I do it？

Below my program code in parts.

SampleClass.cpp

class SampleClass : public QObject
{
    Q_OBJECT
public:
    explicit SampleClass();
    Q_INVOKABLE QDateTime getDatetime();
    Q_INVOKABLE QDate getDate();

};

main.cpp

int main(int argc, char *argv[]){
    QGuiApplication app(argc,argv);
    qmlRegisterType<SampleClass>("sample",1,0,"Sample");

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));
 :

SampleClass.h

QDateTime SampleClass::getDatetime(){
    QDateTime qdate_DEBUG = QDateTime(QDate(2022,9,10), QTime(0,0,0));
    qInfo() << "[DEBUG] QDateTime:" << qdate_DEBUG.toString();

    return qdate_DEBUG;
}
QDate SampleClass::getDate(){
    QDate qdate_DEBUG = QDate(QDate(2022,9,10));
    qInfo() << "[DEBUG] QDate:" << qdate_DEBUG.toString();

    return qdate_DEBUG;
}

main.qml

Window{
    :
    :
        Sample{id: sample} 
        Component.onCompleted: {
               console.log("QDateTime: " +sample.getDatetime())
               console.log("QDate    : " +sample.getDate())
        }
    :
}

Result
Only QDate in qml is conterted to the previous day.

[DEBUG] QDateTime: "Sat Sep 10 00:00:00 2022"
qml: QDateTime: Sat Sep 10 00:00:00 2022 GMT-0700
[DEBUG] QDate: "Sat Sep 10 2022"
qml: QDate    : Fri Sep 9 17:00:00 2022 GMT-0700

fcarney

Use QDateTime, not QDate.

Date in QML also includes time.

Edit: Notice this link does not mention using QDate at all. It is because the conversion is lossy and you will have date errors.