I thought I'd take advantage of the sunny day, and drag out the 14x17 with pinhole attached for test. Focal length was around 550mm, roughly normal FL for this format. Exposure time was 24 minutes. I didn't bother compensating for reciprocity. Turned out well.
No, it is more of a community celebration.
Participation would be a great project for students.
I mistyped the acronym - it is WPPD, for World Pinhole Photography Day.
Here is a link to the charming but clunky website: https://pinholeday.org/
Here is the introduction: https://pinholeday.org/gallery/2020/index.php?epage=intro
Click on the "Exhibition" link to see the gallery for last year: