Time In A Bottle

The bottle, found in the tomb of an ancient, forgotten Pharaoh, sat on his desk.
Having been an archaeologist for over thirty years, John knew there was something different about it.
He opened it, smelling inside. There was musty air, but not much else.
John sneezed, sending up dust from the bottle; a Djinn emerged as well.
"With your breath, you've given a day from your future to the bottle," the Djinn announced. "You may relive any day from your past that you choose."
"Give it back!" John demanded.
"Once given, time is never returned. Employ wisdom when you choose."