QDateTime.fromMSecsSinceEpoch creates an invalid instance

[mkallay]

Fore the following code snippet

quint64 t = 1464808943000;
QDateTime dt;
dt.fromMSecsSinceEpoch(t);
if (dt.isValid())
	cout << "Valid" << endl;
else
	cout << "Not valid" << endl;
QString format = QString("yyyy.MM.dd.hh.mm.ss");
QString timeStamp = dt.toString(format);
cout << timeStamp.toStdString() << endl;

quint64 t = 1464808943000;
QDateTime dt;
dt.fromMSecsSinceEpoch(t);
if (dt.isValid())
	cout << "Valid" << endl;
else
	cout << "Not valid" << endl;
QString format = QString("yyyy.MM.dd.hh.mm.ss");
QString timeStamp = dt.toString(format);
cout << timeStamp.toStdString() << endl;

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The output is
Not Valid,
(empty string)

I am convinced that the number is valid. Entering it in http://www.epochconverter.com/ generates a valid date-time Wed, 01 Jun 2016 19:22:23 GMT.

Using Qt 4.8 on Wincows 8, compiling with Visual Studio 2010.

What am I doing wrong?

Michael