As far as I can tell, Dungeon Day is exclusive to Goodman Games (I could be wrong - I'm more used to Free RPG day later in the year).
It's this Saturday and is honoring the memory of Gary Gygax
If you go to the website on March 4th, you can pick up some free pdf stuff in his honor
https://goodman-games.com/blog/2023/02/25/announcing-dungeon-day-on-march-4th-free-5edcc-adventure-modules-in-print-and-pdf/ (https://goodman-games.com/blog/2023/02/25/announcing-dungeon-day-on-march-4th-free-5edcc-adventure-modules-in-print-and-pdf/)
Oops, missed this. Thanks for posting it though!
Will have to keep in mind for next year. Free DCC adventures! My table's play is based around DCC, so I'm all in.
Free RPG day is coming up in late June. Goodman games has a free module up for that as well.
While I still do mainly DnD 1e, I adapt modules from many systems to play in it. And of course, their TSR Original Adventures Reincarnated hardbacks are awesome indeed.