Answer:
Kings and queens may cling to power and the jester's got his call. But as you may discover the common one outranks them all. What am I?
Who plays when he works and works when he plays?
Taken from a mine and then locked up in a wooden case. I am used by students everyday.
I have green hair a round red head and a long thin white beard.
Light hides me and darkness kills me. What am I?
No matter how little or how much you use me, you change me every month.