To ease the rush hour, our small grocery store has a rule for children returning soft-drink bottles:
NO BOTTLES ACCEPTED AFTER FIVE O'CLOCK
One day, near closing time at 6:30, four young children arrived with bottles. Wanting to put a stop to this habit, I sternly asked each child if he was aware of the rule. Three shook their heads, but the youngest said he knew.
"Why then," I asked, "have you brought me these bottles?"
"I can't tell time yet," he said.