In the middle of a desert stood two men: one was taller, the other one was short. The tall guy says, "I want to use all that science can do to find out when, for the lack of better words to describe it, my 'expiration date' is. C'mon help with me this."
The short guy looks up and replies, "What if, say, your 'expiration date' came yesterday. You're already dead. And I came along granting you with one wish; to live for one more day.
What would you do with that?"
The tall one mumbled a reply, seemingly concentrating with his reasons.
"Instead of finding out how long you'll live, why not live everyday like you already died yesterday, and today is a gift." the short one added as he walked away.