@TheoSys said in QT 6.8.0: Comparison of QDateTime is wrong: Then it's my fault No problem. Datetime with databases is not that easy as it seems so there might still be problems in the drivers even though I spent a lot of time with this 🙂

@Tasha said in QDateTime to a file (Invalid operands to binary expression ('std::fstream' (aka 'basic_fstream<char>') and 'QDateTime'): << + " "; Sort this bit out in your statement.

Just want to summarize the proposed solutions in an orderly fashion so that it remains for the future: @Christian-Ehrlicher: use QDate::addDays() / QDate::addMonths() / QDate::addYears(). [for dates] example: [qDateTime.setDate(qDateTime.date().addYears(XXX)] @JonB : write a global "utility" inline function to do a particular operation you want on a QDateTime. @J-Hilk: make a new class and inherit from QDateTime where you add those convenient setX functions. don't forget to convert the returning objects from the existing functions that return a QDateTime object to the new object, or make a constructor that excepts a QDateTime object as argument, that than can be done implicitly. Thank you all for a fruitful discussion and varied and helpful suggestions!

I found the error. From docs here: https://doc.qt.io/qt-6/qdatetime.html#toString it is reported Note: Day and month names as well as AM/PM indication are given in English (C locale). If localized month and day names and localized forms of AM/PM are used, use QLocale::system().toDateTime(). Correct way to use system locale or a desired locale is qInfo().nospace() << QLocale::system().toString(QDateTime::currentDateTime(), "dd MMMM yyyy hh:mm:ss.zzz");

Now I realized I have to set QDataStream::setVersion to QDataStream::Qt_4_7. I think the problem is solved.

@J-Hilk @aha_1980 I think i failed to see simplicity of this one. thank you for guidence.

@Gojir4 yeah, that's more or less how I used the Component.onCompleted

@the_ said: this (for me) malformed datetime string Well, malformed would be pushing it a bit. If you are in need of a platform independent way of handling the timezone you'd give it as ISO 8601 date time - with the timezone offset; for any other purpose the text representation will be dependent on OS's locale settings. :)

@jsulm QDateTime::currentDateTime is SystemTime

what is your Qt version and target platform?

According to the docs in QDateTime::IsValid: If the timeSpec() is Qt::LocalTime or Qt::TimeZone then the date and time are checked to see if they fall in the Standard Time to Daylight Time transition hour, i.e. if the transition is at 2am and the clock goes forward to 3am then the time from 02:00:00 to 02:59:59.999 is considered to be invalid. QDateTime specified for March 25th, 2007 from 02:00:00 to 02:59:59.999 falls into a " Standard Time to Daylight Time transition hour", i.e. QDateTime::isValid fails, which in turn means that that time does not exist for timeSpec() Qt::LocalTime or Qt::TimeZone. Sorry for using this forum as a rubber duck...

@SGaist said: should post this question to the development mailing list. You'll find the Qt's developers/maintainers (this forum is more user oriented) A discussion on this topic started on that mailing list yesterday, for those who are interested: http://comments.gmane.org/gmane.comp.lib.qt.devel/23437