T RANDS:

On OS X, there is the Date and Time menubar clock that can show the day of the week.

But there's also an application called 'Clock' in the /Applications folder. Launch it and set prefs for 'Digital' mode. You'll get a big fat calendar staring you right in the fat fucking face, and you can put it anywhere you want and make it as transparent as you like (or not at all.)

It won't tell you what year it is, so for those really extended porn-viewing sessions that catapult you back and forth in the space-time continuum, you'll want to go to a third-party app.

Hope this helps.