A man comes up to me at the front desk. He has three items out. He wants to know when they're due. He needs more time with them. I renew them. I print out a receipt with a list of his items and their new due dates. I hand him the receipt. I tell him the new due date. Perhaps there is a short exchange concerning the lovely weather we are having.
"Can you print me out a receipt with the new due dates?" He inquires politely.
"Yes." I say. "I will need to go back in time and give it to you in the past."
He looks into his hand and finds the receipt there already. He laughs. He thanks me.
I am the master of all time.