"Curiouser and curiouser!" cried Alice.
From Alice's Adventures in Wonderland by Lewis Carroll, who wrote it for Alice Liddell who was born on May 4, 1852

Well, Jim, I haven't read any of your books but I'll have to someday because they must be good considering how well they sell.
Nora Joyce, to her novelist husband, on May 4, 1940

The first Sunday in May
On the first Sunday after May Day, in Penzance, Cornwall, UK, people (usually two or three families together) used to visit Rose-hill, Poltier and other adjacent towns, for recreation. They would carry ingredients to make the ‘country cake’ or ‘heavy cake’ made from flour, cream, sugar, and currants. They also visited farmhouses where they ate junket and yoghurt cut in diamonds, and drank tea and punch.

First Sunday in May: Humane Sunday, USA
The first Sunday in May is dedicated to the prevention of child abuse and cruelty to animals. It is sponsored by the American Humane Society.

First Sunday morning of May (Old Style calendar) at Craigie Well, Blackisle of Ross
Many years ago people used to come in large numbers, every first Sunday morning in May, to a sacred spring called Craigie Well. A large briar bush nearby would be covered with threads and bunting, as offerings to the well (similar to oriental prayer flags). The waters, if drunk before sunrise, had healing powers - or so it is said. The whole day had the atmosphere of a fair.