Is void Dialog:: prgCtrl(); declared as slot ?
Qt Code:
  1. void Dialog::prgCtrl()
  2. {
  3. dt= QDateTime::currentDateTime();
  4. qDebug() << "update" << dt;
  5. ui->m_hours->setValue(dt.time().hour());
  6. ui->m_minutes->setValue(dt.time().minute());
  7. ui->m_seconds->setValue(dt.time().second());
  8. }
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Can you see the debug message ?
Another thing is that you can set one second interval for timer, IMHO there is no need for more frequent ui updates in that case.