Behind the laundromat, where there had always been a plain brick wall, Milo found a little door no taller than he was. He ducked inside. A small clockwork librarian slid a card across the counter. Tiny gears ticked inside her chest. "We lend tomorrows here," she said. "Borrow one good day from your own future and spend it today. Just return it by the deadline on the card."

Milo took the card. Tomorrow was his big science fair, and he wasn't ready. "I want a perfect day," he said. "One where everything goes right." The librarian nodded and stamped the card. Right away his backpack felt lighter and his head felt clear. "Spend it well," she said.

The borrowed day was amazing. Milo's volcano worked, his slideshow ran perfectly, and he won first place. But on the bus home he read the card again. "Return by sunset tomorrow," it said in glowing ink. He'd been so happy he almost forgot. Now he had to figure out how to give a day back.

Milo went back to the little door at sunset. The librarian smiled. "To return a day, give one back from your future," she said. "Pick a day you can spare." Milo thought hard. He could give a boring Tuesday weeks from now. Or he could give today, right now, and just go home.

Milo gave back the rest of today instead. The world went gray and still, like someone hit pause. When color came back, it was sunset again and the evening was gone. But his science fair trophy still sat on the shelf. "You kept the prize and paid with your evening," the librarian said. Milo decided that was fair.