42: #GNU is the answer.
It started exactly #FourtyTwo years ago:
https://www.gnu.org/gnu/initial-announcement.en.html
馃巻 馃巼 馃尃
Since I found this nowhere else on the web, I started collecting birthday greetings and other info about gnu 42:
https://www.draketo.de/software/gnu-42
Just write your greetings or a link here or write via IRC in #gnu @ libera.chat to get added to the list.