Sorting was borked in v17, and fixed in v18. It seems there is some bugginess with going from the borked v17 to the working v18, I too have a random set of 3 year old posts that keep appearing. But they are slowly disappearing for me as time passes, now that v18 is properly updating hot sorting.

I have the same, new install of v18 and a lot of my posts are from more than a year ago. Even a lot of the "newer" are over a month old with a single upvote and no comments. It's made "hot" pretty much useless for me.

i think the bug that caused old posts to always appear as hot in 17.4 just made those posts rank higher than other ones, but thanks to 18.0 they're finally getting pushed down. IMO this will fix itself organically.

I really wish, as in !lemmywishlist@lemmy.ml - that each instance could easily adjust these parameters.

I thin it would also be nice as a server operator to have a button to trigger a sort rebuild on demand, not just the internal schedule timer.