Jiffy

"I'll be back in a jiffy."

How do we know how long a jiffy is? How long should I wait for this person to return?

More importantly, is Jiffy Pop really ready in a jiffy? How do I know unless someone tells me how long a jiffy is. All this time, Jiffy Pop could have been lying to us, with their popcorn that takes 6 or 7 jiffies to make.

Can I get a watch that measures jiffies?

How many jiffies will I live?