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?

Wieland

@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.