Answer:
What gets wetter as it dries?
What can travel around the world while staying in a corner?
Marking mortal privation when firmly in place. An enduring summation inscribed in my face.
I am whole but incomplete. I have no eyes yet I see. You can see and see right through me. My largest part is one fourth of what I once was.
When you buy me I am costly, but the only use I have is hanging only. What am I?
No matter how little or how much you use me, you change me every month.