Arguably USENET was actually the beginning of the fediverse, in 1979 :)

The quiz says “On May 18, 2008 🐣 the first public post appeared on a site called identi.ca powered by free software. The idea behind it was that anyone could download the source code and run their own social network connected to other nodes. This was the beginning of Fediverse.”

It doesn’t link to that first post though, because the first ~5 years of identica posts are mostly gone now (modulo what you can find on the wayback machine) 😞

I’m not certain, but if I remember correctly laconica (the software behind identica, which today lives on as GNU Social) instances couldn’t actually federate at the very beginning, but that was its goal from the start so I guess May 18 is a reasonable enough day to celebrate if that is actually when identica launched. I wish I could see that actual first post, though!