Welcome to the Original "Jasmer Challenge". In order to complete this challenge and log your find, you must have logged at least one cache that was placed in every month back to the start of Geocaching (May 2000). Good luck finding the August 2000 caches; there are only four of them in the world.
When I created this almost 20 years ago, I had no idea that it would become a cache that is so widely discussed as it is. I figured it would be a fringe cache that only a few would set out for. I've been tickled over the years to see so many people talk about it, make videos and blog posts about it, and complete the challenge.
The best way to see your progress on this challenge is to use the "My Profile stats" button available at Project-GC, or to run the challenge checker linked below:
I also encourage others to create similar "Jasmer Challenge" caches in their own state so that you can complete the challenge locally and don't have to travel to California to sign the final log. (No more than one per major metropolitan area please.)