The traveller sat on a bench across from me, occasionally checking a time piece on his palm.

"I know you're from the future!" I yelled, "Just tell me what you're here for?!"

He checked his palm again and pursed his lips, then called back. "Two minutes!"

SCIFIFRI - Orion Kidder

In the olden days, before even the internet, the exactly-100-word story was called a "drabble". Almost predictive of short-form social media limits!