It's May Eve. Also known as Walpurgis Night, it marks the six month mark til All Hallows Eve ...
aka Halloween or that beginning of the holiday season !
The day is primarily an observance of central and northern European extraction with dancing and bonfires and the celebrations hold the separate flavors of those locales in which they are held.
These observances are typically either in conjunction with or included within the observance of "May Day" — which in actuality is the next day.
My personal interest in May Eve stems from my late childhood back when werewolves, vampires, and witches were a keen interest.
It seems that the sabbat's may eve focus was that which first brought the notion of May Eve into my thoughts.
The day also remains an homage to my late friend, Chris Gagnon who was an amateur cinematographer back in the oldie but goodie days of 8 mm and of course, Super 8 when we would create all manner of 3 minute technicolor masterpieces in the genre of the macabre.
But alas, those days (and Chris himself) are gone these many years and are relegated to that very personal and private level of my life known as memories.
Regardless, the day is now named for Saint Walpurga, who was canonized on May first in the 870 AD so you can feel safe lighting those bonfires and cutting a rug without getting struck by lightning or getting turned into the undead ... or worse.