Which can be seen by running the following example:

#include <QtCore>

int main(int argc, char *argv[])
{
QDateTime dt1970(QDate(1,1,1970));

QDateTime dt;
time_t tt = 0x7FFFFFFF;
// add 365 days
for (int i = 0; i < 365; ++i, tt += 3600 * 24)

{ dt.setTime_t(tt); qDebug() << dt.toString() << dt1970.secsTo(dt) << (uint)dt1970.secsTo(dt); }

}

secsTo should return an unsigned int, or even better an unsigned 64bit integer.