Visual Display Timer

Hello,

I just started building my new mod, and I was thinking of making a stopwatch that would count the seconds of the world after a certain custom item was right clicked. I want to make it so that once your right click your custom item, the stopwatch will start counting the seconds of your world. I want the seconds to be displayed on the players screen so that they can see it. Maybe above the hunger bar, displaying the seconds. I don't know how to set the stopwatch or set it on the display screen. (I a visual learner so it would be extremely helpful if you sent a picture of your coded procedure so I can get an image of it in my head).