As explained in viewtopic.php?f=6&t=32690 viewtopic.php?f=6&t=32690
it is (currently) not possible to have a mod, that displays the system time.
Steinio recommend here viewtopic.php?f=6&t=32690&p=207474#p207474
the afterburner from MSI
With this program you can configure an OSD which can display time, FPS, CPU, RAM and GPU load and as byproduct overclock your GPU