One week ago I had never heard about clockday. When I read about what it was, I knew I'd had to come up with some content for it, so I did:

http://www.newgrounds.com/portal/view/601051

The idea and the implementation were both conceived on the actual c-day, which I think suits the low-threshold submitting day perfectly. :) And due to it being clockday, it didn't really matter that the logic for solving the riddle was quite obscure. I'm happy to see that people have actually gone through solving it. :)

Any way, I've personally perhaps had too high a threshold for submitting something, so I think clock day is a nice reminder that submitting stuff doesn't have to be that huge a deal. Submitting something small on clockday can be good practice for working with the API etc.