Alright, I think I’ve got it! (and it looks like @Rusty was super close to having it almost 2h ago haha)
I tossed together another calendar organizing by weeks and the dates that we have on the site
If you look at the holiday working weeks as mentioned in the puzzles, and analyze it as binary (0 if that holiday day is not on the site, and 1 if that holiday day IS on the site), you can extract 4 bits of binary per holiday week.
Using the ordering of the puzzle, you can generate 1 byte per line of the puzzle
Putting it all together you can get the word echoes.