Did you use:
/scoreboard objectives setDisplay sidebar sleeping?
And yes, it's case sensitive.

It worked! I decided to try and set the display to sidebar with "setDisplay sidebar"
but the scoreboard does not appear. Is setDisplay case sensitive or am I doing something else wrong?

Thanks!

The one I gave will work in multiplayer as well, it keeps track of every player individually.

Once you've typed that command in chat, you can display the scores on the tab screen using
/scoreboard objectives setDisplay list sleeping

If you still want the more advanced code (which will only make the score go up when a player fully sleeps and thus skips the night) you will have to wait till tomorrow.

It's just for single player mode so I think that will work, just for my own knowledge could you write he more advanced code as well? is that the entire code, I think there is more to make it show on the tab bar or side or over my player head. Can you please right out the whole code? This is the first time I have done any "programming" of this type, or is the rest of it on the wiki somewhere.

Thanks!

/scoreboard objectives add sleeping stat.sleepInBed

This will increment whenever a player enters a bed (whether or not they fully sleep the night away). If you only want it to increment when a player fully sleeps, let me know and I will see what I can do (will be more complex though).