This was the 4th night in a row that I missed 2 hours of sleep because I stayed up too late.
Sure I could look at a clock, but I've come to love in game clocks and prefer those.
I know it's not exactly what you wanted - but download
X-fire. If you're running it in the background while playing the game, you have the option to tack on an easy on the eyes FPS counter, as well as a clock.