QDateTime::currentDateTime timezone issue ?

f222

Hello,

I am currently have a real strange issue with QDateTime::currentDatetime that I cannot comprehend.

We have some code in Qt 5.12 we are porting to Qt 6.9.3. We are developping for Windows using MSVC2019.

The code uses QDateTime::currentDatetime(). This worked fine in Qt 5.12 but in Qt 6.9.3 I have a 3 hour offset on my machine (this doesn't happen to my coworkers).

I can fix this issue by sending the proper timezone to currentDateTime but when debugging it looks like currentDateTime already uses the right timezone:

I've been trying to understand what the issue could be, if there is anything I may have done wrong, but I have absolutely no clue of what is happening here.

Is this a known issue, have I made a mistake or is there something weird happening here ?

sierdzio

Looks like a bug, consider reporting it (but maybe first check with newest Qt version, perhaps it has already been fixed?).

Christian Ehrlicher

Please use a recent Qt version. Also you forgot to create a Q(Core)Application object. This works fine for me with Qt 6.12 (git HEAD):

int main(int argc, char** argv)
{
    QCoreApplication app(argc, argv);
    qDebug() << QDateTime::currentDateTime().timeZone();
    qDebug() << QDateTime::currentDateTime().toString("dd/MM/yyyy hh:mm:ss");
    qDebug() << QTimeZone::systemTimeZone();
    qDebug() << QDateTime::currentDateTime(QTimeZone::systemTimeZone()).toString("dd/MM/yyyy hh:mm:ss");
    return 0;
}
QTimeZone("Europe/Berlin")
"25/09/2026 10:37:14"
QTimeZone("Europe/Berlin")
"25/09/2026 10:37:14"

JonB

@f222
I have a quite different platform/environment from you: Qt 6.10.2 as supplied with Ubuntu 26.04, gcc compiler. I confirm your code works correctly for me --- perhaps not surprisingly since you say yours does not happen to coworkers.

Btw, I thought initially the lack of QCoreApplication might affect it, but I tried mine with and without and it made no difference (still correct). You might just put one in in case it affects your situation.

From https://codebrowser.dev/qt6/qtbase/src/corelib/time/qdatetime.cpp.html#_ZN9QDateTime15currentDateTimeERK9QTimeZone the definition of QDateTime QDateTime::currentDateTime(const QTimeZone &zone) introduced at Qt 6.5 reads:

QDateTime QDateTime::currentDateTime(const QTimeZone &zone)
{
    return fromMSecsSinceEpoch(currentMSecsSinceEpoch(), zone);
}

while the overload without parameter is:

QDateTime QDateTime::currentDateTime()
{
    return currentDateTime(QTimeZone::LocalTime);
}

Knowing this you might want to investigate a bit further why they are giving you different results in your environment and find where the underlying odd behaviour is coming from.