As the PROBLEM statement says:

> it would be difficult for them to quickly prove their authenticity

Yes, you could tell them something that happens tomorrow or the next day. But if time is of the essence and you can't wait until tomorrow, then the Temporal Password helps you _immediately_ demonstrate your authenticity.

They have a time machine. How can time be of the essence?

No more Pym particles.

What if we generate a random number every, say, 5 minutes and maintain a log of them along with their timestamp. Then the time traveler could just look up a few entries immediately after their destination time and convince people by predicting them in advance. Not immediate but pretty quick.

The hash of the next bitcoin block can already be used for this. Easy tamper resistant random number every 10 minutes.

Wouldn’t the butterfly effect change the numbers? If not then the numbers need more entropy and less pseudo.

That would probably break the rules. With the password solution, they're not telling you anything you didn't already know.

What rules? They’re telling you time travel is possible and happens. That’ll be news for me.