title: Subtract 40 minutes from current time
body: <p>I would like to use QDateTime to represent the value of 40 minutes less than the current time as a string.</p>
  
  <pre><code>QDateTime time = QDateTime::currentDateTime() - QDateTime::fromString(QDateTime::currentDateTime().toString("yy/MM/dd hh:40:00"), "yy/MM/dd hh:mm:ss");
  </code></pre>
  
  <p>I tried that. but, It's didn't working.</p>
  
  <p>I want a string minus 40 minutes from the current time and date.</p>