Yep, I've also seen that. But your markup is wrong.
You should use <progress> instead
I am using a kde widget called adjustable-clock which uses html5/css3/javascript and qml to render my system clock.
Here's the source for the current clock I use, it uses a progressbar for the seconds: http://htmlpaste.com/7e957bb5523fa58f98b6657073c4a544942a13c...
QML:
Clock.setRule('#hour', Clock.Hour);
Clock.setRule('#minute', Clock.Minute);
Clock.setRule('#second', 'value', Clock.Second, {'short': true});
