Say it ain't so

"They say that in 7.6 billion years our sun will balloon up to a size larger than the Earth's orbit, thus vaporizing the planet."
"When?"
"In about 7.6 billion years."
"Man! That's a relief. I thought you said '7.6 million years'."

Overheard at the check-out of the supermarket this morning, in the context of 'why worry, be happy', a simplified variant of the preceding old joke: "They say, we're all gonna be dead in a million years."