Rat Catcher’s Day, a little-known holiday, is observed on July 22 in the U.S., and it celebrates the myth of the Pied Piper of Hamelin (Germany).
According to lore, residents of the German town of Hamelin hired a strangely dressed man to rid their village of rats by playing his pipe. But when he finished the task, the townsfolk refused to pay— so the Pied Piper returned while they were in church and disappeared with their children.
The U.S. holiday is celebrated on July 22, the day that 16th century scribe Richard Rowland Verstegen determined was when the Pied Piper made off with Hamelin's children, according to Chase's Calendar of Events.
Additional source: National Geographic