Previously I celebrated July 22 as Pi Approximation Day (22/7=3.14. . .) But since I’ve jumped ship and started celebrating Tau rather than Pi (see June 28,) today I will be celebrating Rat-catcher’s Day.
Rat-catcher’s Day is celebrated on 26 June or 22 July, commemorating the myth of the Pied Piper of Hamelin. The confusion of dates is because the Grimm Brothers cite 26 June 1284 as the date the Pied Piper led the children out of the town, while the poem by Robert Browning gives it as 22 July 1376.
Anecdotal reports suggest that European rat-catchers would raise rats instead of catching them to increase their payment from the town. Jack Black was a rat-catcher and mole destroyer from Battersea, England. When he caught any unusually coloured rats, he bred them to establish new colour varieties.
Black would sell his home-bred domesticated coloured rats as pets. The more sophisticated ladies of court kept their rats in dainty gilded cages and even Queen Victoria kept a rat or two.
Summarized from Wikipedia.