Qt5.6 QDateTime::fromString ERROR

[ReinaldoJr]

Hi,

QDateTime dt=QDateTime::fromString("2016-10-16 00:00:00","yyyy-MM-dd hh:mm:ss");

dt.isValid()==false!!!!

Using Qt5.6, Fedora 17, x86
This is a bug?

[A Former User]

@ReinaldoJr Works for me. Qt 5.6, x86_64 Linux

[Ratzz]

@ReinaldoJr
i just tried

    QDateTime dateTime2=QDateTime::fromString("2016-10-16 00:00:00","yyyy-MM-dd hh:mm:ss");

    bool txt= dateTime2.isValid() ;
    qDebug()<< "bool" <<txt;

    bool true;

Works for me as well Qt 5.5.0 ,Kubuntu 14.04

[ReinaldoJr]

Thank you for help
Strangely the error persists ... on different machines (Qt5.6 Fedora 17 x86, Qt5.6 Fedora 17 x64) will install another OS...

#include <QCoreApplication>
#include <QDateTime>
#include <QDebug>

int main(int argc, char *argv[])
{
 QCoreApplication a(argc, argv);

 QDateTime dateTime2=QDateTime::fromString("2016-10-15 00:00:00","yyyy-MM-dd hh:mm:ss");
 bool txt=dateTime2.isValid() ;
 qDebug()<<"Dt0"<< "bool" <<txt;

 // :-(
 dateTime2=QDateTime::fromString("2016-10-16 00:00:00","yyyy-MM-dd hh:mm:ss");
 txt=dateTime2.isValid() ;
 qDebug()<<"Dt1"<< "bool" <<txt;
 // :-(

 dateTime2=QDateTime::fromString("2016-10-17 00:00:00","yyyy-MM-dd hh:mm:ss");
 txt=dateTime2.isValid() ;
 qDebug()<<"Dt2"<< "bool" <<txt;

 return a.exec();
}

Result:
Dt0 bool true
Dt1 bool false
Dt2 bool true

[SGaist]

Hi,

Working fine on OS X also.

What timezone are you in ?

[ReinaldoJr]

Hi,

UTC offset (ISO 8601) −03:00 = America/Sao Paulo (LMT)

[ReinaldoJr]

It worked

We use the time the statement(Until then I had never given problem!):

QDateTime dt=QDateTime::fromString("2016-10-16 00:00:00","yyyy-MM-dd hh:mm:ss");
//dt.isvalid=false!!!

So he went back to work:

QDateTime dt=QDateTime::fromString("2016-10-16 00:00:00","yyyy-MM-dd hh:mm:ss");
dt.setTimeSpec(Qt::UTC); 
//dt.isvalid=true!!!  is ok!!!

Thank you all

[Paul Colby]

Just building on what others have already said... :)

@ReinaldoJr said:

UTC offset (ISO 8601) −03:00 = America/Sao Paulo (LMT)

Just for clarity, you might be at -03:00 right now, but thanks to daylight savings, you'll jump to -02:00 at "2016-10-16 00:00:00" (local time), which means you're never really at that point in (local) time.

QDateTime | Daylight-Saving Time (DST) says:

QDateTime takes into consideration the Standard Time to Daylight-Saving Time transition. For example if the transition is at 2am and the clock goes forward to 3am, then there is a "missing" hour from 02:00:00 to 02:59:59.999 which QDateTime considers to be invalid. Any date maths performed will take this missing hour into account and return a valid result.

In your case, that "missing hour" is from "2016-10-16 00:00:00" to "2016-10-16 01:00:00".

Depending on what you're trying to do, you should either prevent your users from entering invalid local times, or use UTC as suggested above.

Cheers.

[kshegunov]

@Paul-Colby

In your case, that "missing hour" is from "2016-10-16 00:00:00" to "2016-10-16 01:00:00".

I think the transition is always at 2 AM local time. So you'd always miss 2:00, i.e. the clock jumps from 1:59 to 3:00.

[Paul Colby]

@kshegunov said:

I think the transition is always at 2 AM local time.

Not according to http://clock.zone/america/sao-paulo

The timezone America/Sao_Paulo switches to DST on Sunday, 16 October 2016 (12:00 AM). New GMT offset will be GMT-2 hour(s) (BRST). Clocks will be set +1h.

It is always 1am forward, and 2am back where I live :)

Cheers.

[kshegunov]

@Paul-Colby

Huh, this is confusing. Can't they make it the same everywhere ...
EET (+2 UTC), where I live, switches forward at 2 AM local, and I think CET (+1 UTC) also does the same. Anyway, I suppose I'm just wrong in my extrapolation, happens too often I'm afraid ... :)

Kind regards.