Satanic Holiday -Walpurgis Day- from the evening of April 30 until May 1.

In the Satanic Bible, Mr LaVey wrote: "After one's own birthday, the two major Satanic holidays are Walpurgisnacht (May 1st) and Halloween.”

“Walpurgisnacht” which is a German term for Walpurga’s night that eventually became synonymous to the Night of Witches. It is a spring festival traditionally celebrated in many parts of Central and Northern Europe. It runs from the evening of April 30 until May 1. It is scheduled exactly 6 months before Halloween Eve.

https://www.express.co.uk/news/weird/1038900/halloween-2018-church-of-satan-anton-lavey-occultist-satanism-devil

http://www.theopenscroll.com/hosting/SatanicCalendar.htm