I was curious too. Joe and Jennison started GAAD 12 years ago from a discussion on a forum/blog post (https://accessibility.day/about/). So I suppose if you want to put 10 years into trying to get something mainstream, you too could start a day for something that folks weren't paying enough attention too ;).

That said, I'd say Global Accessibility Awareness Day is mainstream enough at this point to be called out, given that it's being mentioned at the bottom of Apple's press releases for accessibility (https://www.apple.com/newsroom/2023/05/apple-previews-live-s...)